Pool Shock: When & How Much?

pool shock when and how much

The topic of this post might be shocking to some people…that’s because we’re talking about pool shock! There are lots of questions about why you should shock, when you should shock, and how much shock to use. Today we will discuss the answers to those questions, and give you a better understanding of how pool shock works.

The process of shocking is basically adding a highly concentrated dose of chlorine to the pool water to prevent or resolve problems. Shock will help prevent the growth of algae, bacteria, and chloramines, by raising the level of free available chlorine. It will also help remove those substances if they have taken up residence in your pool. 

Why Shock the Pool?pool care questions

While there are many problems that can be solved by shocking your pool, there are three main ones that we will discuss today. We like to call them the ABCs of Pool Shocking:

  • Algae: This pesky organism can wreck havoc on your pool if left to its own devices. Adding shock to your pool regularly will keep algae out of your pool water. Shock is also the main way to rid your pool of algae if it has taken root and spread. 
  • Bacteria: Similarly to algae, bacteria is definitely not something you want in your pool water. Not only can bacteria damage your pool water, leading to the need to drain your pool, but it can be very harmful to swimmers. Pool shock will prevent and remove bacteria like cryptosporidium, E.coli, and giardia.
  • Chloramines: Also known as Combined Available Chlorine (CAC), chloramines are created when Free Available Chlorine (FAC) combine with contaminants such as dirt, rain, bodily fluids, and pollution. While there will always be some chloramines present in swimming pools, an excessive amount is undesirable. Once again, pool shock is the go–to way to ride your pool of too many chloramines.

1. Prevent & Remove Algae 

Shock is a great way to rid your pool of algae, in addition to using an algaecide. Pool shock, in the right amounts, will destroy all types of algae by slashing through their slimy outer shells, and disrupting their cellular processes.

Depending on how severe the algae growth is in your pool, you may need to use a large amount of pool shock. Light green or isolated algae may only require 10 ppm (parts per million) of added chlorine to eradicate. Medium green or yellow blooms may need double the dose. For dark green or black algae, adding enough pool shock to reach 30 ppm may be necessary.

Shocking the pool to 30 ppm of free chlorine, with proper pH, eradicates most algae. For best results, vacuum the pool before shocking, and brush the entire pool before and after shocking. Filter nonstop, backwash as needed, and use a pool clarifier after the treatment process to clear up your pool water.

2. Prevent & Remove Bacteria

Stubborn bacteria, viruses and parasites can live in pool water and cause all sorts of problems. Bacteria like cryptosporidium, E. coli, and giardia are more common in public swimming pools where the water is filled with organic material. Proper, routine sanitation and filtration will likely prevent and remove most pathogens, but if you want to be sure, a good pool shock is in order.

bacteria

The amount of shock needed to remove bacteria depends on the level of bacteria present in the water. Test the pool water for bacteria with a bacteria test kit. It’s a good idea to start by adding enough shock to raise your pool water’s chlorine level to 30 ppm.

How much chlorine is needed to kill bacteria in swimming pools? It depends on the type of bacteria, and the extent of the contamination. Most types of bacteria found in pools, such as E. coli, are fairly easy to kill with just 2–3 ppm of chlorine. However, the CDC recommends that for pool fecal incidents involving diarrhea, maintain a level of 20 ppm for 13 hours prevent the development of cryptosporidium.

3. Destroy Chloramines

Although it seems counterintuitive, when your pool smells strongly of chlorine, chloramine bonds are likely at a high level, and a good pool shock is needed.

Using a DPD test kit will allow you to measure both FAC and Total Available Chlorine (TAC). Shock the pool to a level 100x greater than your chloramine level. For example, if your chloramine level is at 0.3 ppm, add enough shock to reach a level of 30 ppm. Raising the chlorine level in your pool will break apart the chloramine bonds, and remove them from the water.

Below is a chart detailing how much shock to add for chloramine removal. Remember, this chart assumes a good pH, and a relatively low Cyanuric Acid (CYA) level. More shock is needed for higher levels of stabilizer in the pool, and for pH levels above 7.5.

Amount of Chlorine to Reach Breakpoint Chlorination

(Assumes pH of 7.5, CYA of 30 ppm)
Dosage per 10,000 gallons:

Chloramine LevelCal HypoCloroxDichlorLithium Hypo
0.115 oz150 oz18 oz28 oz
0.345 oz450 oz54 oz84 oz
0.575 oz750 oz90 oz130 oz

Amount of Chlorine to Reach Desired Concentrations

(Assumes pH of 7.5, CYA of 30 ppm, Temperature 75ºF)
Dosage per 10,000 gallons:

Desired Chlorine LevelCal HypoCloroxDichlorLithium Hypo
10 ppm21 oz228 oz25 oz39 oz
20 ppm42 oz455 oz35 oz78 oz
30 ppm63 oz683 oz60 oz117 oz

Like our charts mention, 20 ppm requires a good pH level and a relatively low level of Cyanuric Acid. A tepid temperature of 70-80 degrees is also assumed. High pH, high stabilizer or high temperatures will require a higher concentration of chlorine and/or a longer reaction time to effectively remove bacteria in swimming pools.

How Much Pool Shock Do I Need?

Breakpoint chlorination is a level of chlorine at which point molecular bonds break apart. Conveniently, this is also when the water removes chloramines, algae, and pathogens.

For most situations, a level of 30 ppm of chlorine will reach the threshold of breakpoint chlorination needed to restore order in the pool.

Here’s a pool shock treatment chart to determine the amount of pool shock necessary to raise the chlorine level above the breakpoint threshold, usually around 30 ppm.

This quick reference chart is based on 10,000 gallons of water:

Pool Shock TypeIncrease by 10 ppm
Calcium Hypochlorite1.3 lbs
Sodium Hypochlorite3.5 qts
Lithium Hypchlorite2.5 lbs
Dichlor1.5 lbs

For example, using the table above, a 20,000 gallon pool would require 7.8 lbs of cal-hypo to increase the levels by 30 ppm.

Check for proper water balance, especially pH in the range of 7.2–7.6, before adding the shock to the pool. A high pH of 7.8–8.2 can render up to half of your pool shock completely inactive.

Proper filtration and circulation are key factors for proper shocking — pool shock doesn’t do it all alone. Filter the pool water after treatment to remove any remaining particulates. 

How to Shock Your Pool 

Shocking your pool is a fairly straightforward process. But it is important to follow the following prep steps before you dive into shocking. Poorly prepared pool water can render the shock ineffective, failing to address the underlying issue.

  1. Clean Your Pool: Leaves and debris on the floor and surface will waste your chlorine’s killing power as it attacks these organic materials, rather than the ABC problem that we are trying to correct.
  2. Lower the pH: Chlorine is very sluggish at high pH levels. At a pH of 8.0, less than half of the chlorine you add to the water will convert to hypochlorous acid, the killing form of chlorine. Lower the pH to 7.2 before shocking.
  3. Read the Label: We have many types of pool shock, all with slightly different dosages. For some pool shock, dilution in a bucket is necessary to dissolve the granules and prevent damage to pool surfaces.
  4. Add the Shock: Distribute the granular chlorine throughout the pool surface with the pool pump running. Be careful not to spill any on your clothing, or on the pool deck, and add the shock slowly and close to the surface of the water. On days with high winds, refrain from shocking your pool to prevent the wind from blowing away the shock from your pool water.
  5. Brush the Pool: This helps distribute the chemicals, and removes the layer of dust and film on your pool surfaces. A good brushing, vacuuming, and backwashing should follow an algae shock treatment.

Pool shock can also be used in smaller amounts as a quick booster to your chlorine level. This practice is called super chlorination. Usually just a pound of shock will bring chlorine levels up from zero to a range that will prevent problems. Waiting for tablets to dissolve could take too long, so if you find your chlorine level at zero, use a pound or two of pool shock to bring up the chlorine level quickly.

The moral of the story is that you have to test your pool to know when to shock. Shocking monthly or even weekly is overkill in many cases.

205 thoughts on “Pool Shock: When & How Much?

  1. How much shock do I need for a 17,000 (27 feet Dia) gallon above ground pool? I do put 1.5-2 lbs of shock every week. However I am fighting a high CYA (100-110) which creates a problem with algae growth. The shock that I use has CYA. I use diclore (sp). I use 2-3 3 inch tablets.

    • Hi Donald, yes your shock level seems ok, but maybe too frequent, unless you are fighting algae, or bacteria or chloramines or other need to shock weekly. At 100 ppm CYA, I would recommend that you drain and refill half of the pool, and shock less if possible, and eventually switch to using Cal Hypo shock, in the evening.

  2. my pool is 13 foot round 33 inches high, i struggle with numbers, (I’m like number blind if there is such a thing) how much shock treatment should i put in? (it does need it after having my grandchildren all bouncing about in it for some of the two weeks its been up, its slightly cloudy, i have read so much stuff about this that and the other but just need someone to tell me what to do with quantity,

    • Hi Liesa, for your pool size (2000 gals), use 1/4 cup or 4 oz to shock the pool, and if the water is green or very cloudy, you could use 6-8 oz of granular Cal Hypo 65% available ‘pool shock’.

    • I had the same problems until I read what the experts are saying thoroughly.
      Step 1. Calculate the volume of your pool. I thought mine was 12000 gals. Turns out it’s closer to 20,000.
      Step 2. Assuming your pool is cloudy with algae. Shock your pool. You need to raise your chlorine level above 30ppm. So for my pool that’s about 8 pounds of shock.
      Step 3. Brush the whole pool. IF chlorine is zero the next day, you missed the mark, shock again.
      Step 4. Filter until your pool is clear. Backwash every morning. Your pool will clear in 24-72 hours.
      Step 5. Vacuum the brown dead algae out of the pool every day

  3. i have an intex pool 13ft33in. I have been putting tablets in floater and running filter for 6 hrs a day all was good until we had a rain storm. Pool temp is also 89. Pool is now cloudy and am asking if i should shock it ….if so what is best and how much should i use.

    • Yes, shocking the pool after a rainstorm can help restore order. You can use regular pool shock or non-chlorine shock, both are good. As far as how much to use, look at the label for dosage, and it will probably be 1 lb per 10,000 gallons or something like that… then do the math, to calculate the amount to use for your pool. (you need to know how many gallons is in your pool)

  4. Matt Cullen

    Hello,

    Constant green algae battle during summer

    33500 Gallon combo Plaster Pool and Spa
    Pentair D.E. Filter 60 sqft (full replace with new grids a year ago)
    Whisperflow 2hp
    Two inch PVC supply and drain lines
    Polaris Robotic IQ P965 ran once a day
    3” Inline Chlorinator
    No Heater

    Constant green algae battle in summer.

    Unfortunately the previous owner didn’t take care of, the plaster is severely pitted but not leaking, In need of future replastering sooner than later once $$$ permits

    We live in North Texas where temperatures this week are averaging close to 100 degrees

    Our Black Labrador Retriever swims multiple times a week.

    Wife, 10 year old daughter, and I swim about once a week.

    So with all of above taking into consideration – What is your recommendation for shocking to keep algae at bay.

    How much shock? and How Often?

    Is there a better time of day to shock?

    We run pump 12 hours a day. What time is best?
    Morning to evening or evening to morning?

    Any other recommendations.

    Thank you for any feedback!
    Matt

    • Hello Matt. The first thought with the ‘constant green algae; is that you may have phosphate contamination. levels over 300 ppb (parts per Billion), should be treated with a phosphate remover. Levels over 1500 ppb may need treatment more than once. The phosphates may be entering from the lab swimming, but can be other sources like fertilizer, overhanging trees, heavy rain washing in soil/mulch, and from use of some stain & scale chemicals that contain orthophosphates. The plaster is also a problem, when it has etching and pits, it is easier for algae to get a foothold. A method that may be cheaper and faster, is to drain the pool and pressure wash the pool and tile, then bleach wash the pool and tile, and then refill. Then you can really remove it from the plaster, and start with fresh water, with no phosphates/nitrates etc. If that is not possible then get phosphate test strips and a bottle of PhosFree, and start a regimen of using Poly 60 Algaecide each week in maintenance doses, and also shocking weekly if needed, but several days after adding the algaecide. If you see no algae, and chlorine levels are high and pH levels are low, you can skip the weekly shocking. 12-hours per day sounds good for your filter, best time to run it is during the sunlight hours. Happy Fourth!

  5. I have a 12ft x48 pool which is like 3400 gallons . How much shock and other chemicals should I use ? First time pool owner .

    • Hi Tony, click on over to poolcalculator.com, and you can see for yourself! Just enter your pool gallons, upper left and you can see exact doses for various chemicals.

  6. Hi- I have a 15 x 48″ intex easy set pool.. Should I use 7.2oz of shock for the pool?I I bought a oxidizing shock and swim. Will that make it safe for swimming?

    • Pool shock does make water safe for swimming, when the water is balanced with good pH and alkalinity and chlorine stabilizer. You should wait to swim after shocking the pool, and always remove any solar blankets or covers on the pool when shocking. 7.2 oz sounds about right, if your pool is about 4500 gallons? Most pool shock has dosage listed as “Add 1 lb. (16 oz) per 10,000 gallons” or something similar. As a pool owner, you have to know your pool gallonage by heart, and do the math calculation to convert the dosage to a smaller (or larger) pool.

  7. I have a 16×48 5200 gallon pool..should I use 1- 3 in. Chlorine tab per day? And also I have some pool shock that is liquid (splash) brand. It says 52-104 oz. Of product per 10000 gallons to yield 5 to 10 ppm available chlorine by weight….no clue what that means..can you possibly tell me how much shock to use in the liquid form for 5200 gallons?

    • Yes, add 1/3 gallon of the liquid for a good shocking. The 1 tablet is likely perfect, a test kit will tell you for sure though, as chlorine use not only depends on pool size, but water temperature, sunlight, bather load and organic debris, and pH level. But 1 3 inch tablet is likely fine, just remember to replace it before it dissolves completely, in 5-7 days, usually.

  8. Rafael Diaz Jr

    I have a 5,400 gallons circular above ground pool. I keep the water clean. Do I need to shock the pool? How much shock do I need? I read that depends of where you leave. I leave in El Paso,TX and the weather is over 95F in summer and my kids use the pool at least 4 times a week. I’m new on this and I’m trying to do the best I can to keep it stable.

    • Hi Rafael, shocking is needed for every pool, but only when needed… A-B-C, to control/kill/remove Algae, Bacteria, and Chloramines or Cloudy water. A lot of people are told to just “shock the pool every week.” which might be overkill, but if you lay awake at night worrying about germs and parasites in the pool water, it can help you relax. If everything looks great in the water, and there is no algae seen, and if your kids are fairly clean people 🙂 and don’t use the pool as a bathroom, then shocking once or twice per month may be enough. But if they have even small amounts of ‘fecal matter’ on their backsides, bacteria can begin to grow in the pool. Animals also bring bacteria, pets and wildlife. Often heavy rainstorms can wash in contaminants that pool shock can remove. Your daily chlorination, with tablets will kill most of the germs, but not all, and an occassional oxidation of the water is important, to allow the tablets to stay on top of things. Shock is also useful for those times when the chlorine level accidentally gets too low, or pH gets too high, or the filtration or circulation has been interrupted due to power or mechanical problems, shock allows you to raise the chlorine level fast, without waiting for tablets to dissolve, which could take all day, and by then things are starting to grow.

  9. I have a blow up pool it’s 665 gallons how much shock and chlorine do I use? Do I use tablets or liquid chlorine? I have liquid shock left from last year when I had a bigger pool can I still use it?

  10. I have a 3000 gallon aboveground pool how much shock should i use the pool is round

    • Use 1/3 of a bag, or pound, about 5 oz, when the water is clean and clear. If you see algae double the dose, and if it’s lots of algae, triple the dose to an entire bag, or change the water in the pool. Pre-Dissolve the shock before adding to a vinyl pool, so that chlorine granules won’t etch or corrode the soft surface.

      • First time pool owner here🥴 I have a 3300 gallon pool. I dissolve the shock into a bucket with water…How much water do I use with the shock mix???

        • Use a 5-gal bucket, and fill it with pool water, add the shock and stir for about a minute. Then pour into the pool, being careful with the remaining particles, which may need another soaking to dissolve fully.

  11. patsy mobley

    my pool was clear then covered with a warmer and it turned green. 4500 gal. of water. How much shock should I use?

    • Hi Patsy, first make sure the pH is not high, over 7.8, if so add some pH down. Then use 1 lb of pool shock for a light to medium green, or 2 lbs for a heavy green color, where you can’t really see the bottom. After 5-10 mins, if it has not turned a blue-ish grey color, add more shock, until it does… Run the filter all night. With a vinyl pool, be sure to pre-dissolve the shock in a bucket of pool water, before adding.

      • Betty Reed

        I have a 1400 gallon intex 12x 30 above ground pool. How much shock should I put in the pool and how often?

        • Hi Betty – it depends on the strength of the particular shock, but every type of pool shock will list the dosage amount, expressed usually as “1 lb. per 10,000 gallons” – for example, although it will vary among strengths. And in your case, for a pool of 1400 gallons, you are 14% of 10000 gallons. So you would multiply the dosage amount by 0.14 – or 16 oz. x 0.14 = 2.25 oz. I also like to use poolcalculator.com for small pools, it’s easier to ‘over-shoot’ the mark with a smaller pool.

  12. I have a 45000 gal salt filter pool. How much salt and shock should I be using on an average

    • Hi Walter. Salt systems require an initial large dose of salt, and then annual booster amounts to make up for backwash water, splash out and refill water used, which dilutes an lowers the salt level in the pool. Some salt systems will also shock the pool, but that can place a big demand on the salt cell, and perhaps shorten it’s life, so for that reason I’ve always thought it best to use granular pool shock (or non-chlorine shock), when shocking a salt pool, and not hit the ‘shock’ button on the controller. Most shocks are 1 lb per 10,000 gallons, so for your 45K pool, use 5 lbs when the water looks clean and clear. IF you are killing algae, double the dose, or for severe algae triple the dose (or more if you a swamp on your hands). If the pool looks great, just shock once per month, with 5 lbs, to kill any stray bacteria and remove chloramines, aka combined chlorine. For the salt amount, it depends on the recommended salinity level of your salt system, but let’s say it calls for a level of 3000 ppm salt. Initially Add 250 lbs of Salt, per 10,000 gallons, to reach 3000 ppm (from 0), or for your pool, 1125 lbs of Pool Salt. Or another way to look at it is – add 8 lbs of pool salt, per 10000 gals, to raise salinity level 100 ppm. Every month or so, you should check your salt level and add a booster shot if you are getting close to the minimum level recommended by the manufacturer. Be sure to add “Pool Salt” and nothing else, which can contain staining impurities and metals.

  13. MICHAEL WELCH

    I have similar size pool about 1700 gallons 12 x 30. How much 1in tablets should be in the floater?

    • Hi Michael, probably just 1 3-inch tablet, or half a dozen 1-inch tablets. Your test kit will tell you for sure. If the chlorine level is 2-3 ppm, use less. If the chlorine level is 0-1, use more. Use enough to establish a constant and consistent level of 1-2 ppm, which can vary… depending on weather, temperature, bather load and debris load, and filtration effectiveness, and the use of any other supplemental chemical…

  14. Hi I have 1700 gallon above ground pool. Should I use shock in it for a weekly cleaning, and if so how much.

    • For such a small pool, the need for shocking is greater than for larger pools. I would shock smaller pools, with smaller, less effective filters and less of other things as well… so yes every week to ten days, I would shock that pool. You can use non-chlorine shock, if you are not trying to kill algae, or any extreme contamination or water problems… The normal shock dosage for a clean and clear pool is 1 lb of granular per 10,000 gallons of pool water. Since you are only 17% of 10,000 gallons, you could use 17% of the bag or 2.72 ounces, and up to 4 oz (half cup) would be ok as well. Dissolve it into a bucket of clean water, and pour around the edge of the pool, with the filter running. Before shocking, check pH level, and add pH decreaser if 7.8 or higher. NOTE: Store open bag of shock with great care, to prevent contamination from moisture, bugs, dirt, or any-thing. Use paper clips to close tightly, and store inside of a tupperware type bowl, by itself.

      • Hello. I also have a 12×30 pool
        Why do I need to dissolve the shock in a bucket of water 1st? My bag of instructions say to throw granules directly into pool. Also, how much granules for algea and how much granules for metal and stain, and how often? Thank you!!

        • Fran, some more expensive shock types which are very fine, or non-chlorine shock can be added without pre-dissolving, but Cal Hypo pool shock should be, as the granules, if sitting on the pool floor, could damage the vinyl, or bleach the color.

  15. Lorraine casteel

    How much shock treatment for a blow up vinyl pool. 900 gallon

    • Hi, if the water is mostly clean and clear, just 2 oz of the chlorine powder would be sufficient. Pre-dissolve the chlorine in a bucket of water, and then pour into the pool. Be careful with the opened bag of shock. Clip it tightly closed, and store it in a plastic tupperware container, to prevent spills and contamination from dirt, insects and moisture.

      • Rebecca Lacy

        Hi i have the same pool but have never used chemicals, had it for two weeks and it is green. I see you said to use 2 oz of shock, but should I use other chemicals with it. The test strip currently reads 8.4 ph, 0 chlorine, 0 alkalinity, and 0 stabilizer.

        • Hi Rebecca, if your inflatable pool is green, I would suggest draining the pool, scrubbing the walls (no soap) and refilling with fresh water. Then keep a constant and consistent level of chlorine in the water, with a good pH level of 7.2 to 7.4, where chlorine is most potent. High pH and low chlorine is a recipe for bacteria that can make swimmers sick. The best way to consistently chlorinate is with 1″ chlorine tablets and a small chlorine floater, or if that is not possible, add small amounts of granular or liquid chlorine twice per day, testing to determine the sweet spot for dosage and frequency. Use pH decreaser to keep the pH from rising above 7.6.

  16. CoolBreeze

    I have a 24’ round 54” heigh pool, getting ready to open for the season. How much shock and other things I need, to get it ready

    • Hey there, your pool is about 13,500 gallons, so I would plan on 12 bags of shock and 25 lbs of 3″ chlorine tablets for the season. You may also want a bottle of Clarifier, and a bottle of Algaecide, both added every week or two. Then depending on the water test results, you may or may not need: Cyanuric Acid (Stabilizer), Alkalinity Increaser, Calcium Hardness Increaser, pH Increaser/Reducer.

  17. Priscilla Estrada

    Hi there I have a 18×48 size pool. How many bags of 1 pound shock do I use to first open it?

    • Hi Priscilla, a pool your size has about 8000 gallons. Most shock dose is 1 lb per 10,000 gallons, so use 1 lb when the water is clear or a bit cloudy. If you have algae, use 2 lbs or 2 bags. If the algae is severe, add 3 or possibly 4 bags.

  18. I have shocked my pool but it’s still green can I shock it again

    • Yes! Check the pH first, and make sure it’s on the low side, 7.2-ish, where chlorine is most potent. Depending on how green it is, use, 2, 3 or even 4 lbs of shock per 10,000 gallons (for light, medium or heavy algae)

  19. Hi, I have taken a sample of my pool water to a pool supply company twice now it a two week period. They keep telling me that all my levels are reading normal, but my pool water is cloudy. This is an 18 foot, above ground pool. The sand filter is working fine, and I have shocked it a few times now. I don’t know what I’m doing wrong, or missing?

    • Hi Sara, if you chlorine level is fine, and your ph and alkalinity and other measures are also within range – it must be the filter. Either not operating long enough each day, or the sand needs to be changed, or the filter valve or filter is operating improperly and bypassing some water, around the filter and back to the pool. If you have a small sand filter (under 18″ dia), you may need to change the filter sand every 1-3 years, as the sand bed is just not that deep. You can also use a filter cleaner, to try to remove oil and scale, which reduces sand filter effectiveness.

  20. Anna Newcomb

    I just put shock in my pool, I just sprinkled the loose crystals around my pool slowly , Was I supposed to pre-dissolve them first

    • Anna, only if you have a vinyl liner pool. When chlorine crystals lay on vinyl, it could bleach them or remove some of the colorant, and could also corrode the vinyl a small bit, before the granule dissolves fully. Not usually once or twice, but doing it over time can fade or damage vinyl. Vinyl pool owners should pour the crystals into a clean 5-gal bucket (already) filled with water, and then stir for 30-60 seconds to dissolve. Pour around the pool, and be careful as the bucket empties, not to pour in undissolved granules, but refill again, and stir again, then pour into the deep end, hitting with a brush if necessary to help disperse and dissolve.

  21. Sara Moore

    Hi. If my pool is 450 gallons – how much shock and what type of shock should I use?

    • 450 gals is not a very big pool! You can easily over-chlorinate it to the point of being unhealthy. I would use regular household bleach for a pool so small, or use spa chemicals. If using 6% bleach, I would shock with 10 oz., to achieve about 10 ppm. For complete sanitation however, shocking to 30 ppm may be necessary, in some cases of severe algae or for some forms of bacteria. You can use Bromine tablets and non-chlorine shock, which is a nice sanitizer combo. Spa chemicals or Spa Shock, in particular is safer because they are sold in resealable containers and because they are labeled for use with spas of 300-500 gallons.

  22. Hi!! I accidentally used a 1lb shock treatment that’s for a 10,000 pool in a 6200 gallon pool, it still hasn’t dissolved yet and My kids have already swam in it, dont know How long should I wait to swim In it and and is it safe? I don’t know how much I should add and wait until it dissolves? Thanks!!!

    • Hi Edith, it’s ok to overchlorinate occasionally – the level will come down in a few days. The concern about swimming after using granular chlorine is primarily focused on undissolved granules that may get into eyes, or other sensitive areas of the body, causing irritation or burns. Your shock brand should say on the bag label, when swimming is considered safe, generally less than 24 hours. In some cases, you can allow limited (short time period) swimming – with heads above water, or wearing swim goggles, after waiting less than 24 hours, perhaps 3-4 hours. Most people shock in the evening, after swimming is done for the day, and also when the sun is not shining on the pool, which degrades chlorine.

  23. I’m new to pool maintenance and I just bought a small intex above ground pool, holds about 1000 gallons. I read that I could just start off with 4 oz of regular bleach, and then for regular maintenance, use a dispenser with 1″ trichlor tablets that dissolves in about a week? However, I mistakenly bought the 3″ 90% trichlor tablets that is more suited for 5000 gallons per tablet. Can I still just cut up each tablet into 4 parts and put one part in each week, adjusting the floater collar to the minimum to reduce water exposure?

    • Hi Sara, yes the 3″ tabs are the same chemical as the 1″ tabs, so you could break them with a hammer into 2 or 3 pieces if necessary, but probably you could just use a whole tablet, and just close the baffle or collar almost completely to reduce flow. Test the water a few days later, if chlorine is more than 2.5 ppm (or too high), then it would be best to use 1/2 tablet.

  24. I have the same pool. Is there a need to shock the pool for its first use Or what’s the best treatment for first time use

    • Hi Chance, the reasons for shocking a pool are (I like to say) A-B-C, A stands for algae, shock if you see visible algae growing. B stands for bacteria, which you cannot usually see, but maybe the water smells bad or looks bad, or you just had 20 bad looking, smelly people in the pool 🙂 and you suspect that the pool may be harboring some bacteria, or C we may shock the pool for Chloramines (aka combined chlorine), which is when Free Chlorine combines with a ammonia or nitrogen or other to make a compound that smells strongly of chlorine, and turns swimmers eyes red. Chloramines can be tested for with a DPD test kit (TC-FC=CC). C can also stand for cloudy water. So… if the water out of the tap tests well, looks good and you have no reason to suspect A, B or C – then no need to shock at this time. But some people may do it anyway, just to be sure that the water has been disinfected, and is sanitary for swimmers. And if it has taken several days to fill the pool, shocking would also be a good idea, since just one day in these summer temps, will begin to grow microbes and bacteria in the water.

  25. I have a 18X48 how much shock and Chlorine do I need and how long do I have to wait

    • To figure out pool gallons – the formula is L x W x Avg. Depth x 7.5 = gallons or for round pools it is Pi x radius squared x Avg Depth x 7.5. Or for your pool, about 7500 gals. Then you simply consult the packaging for the recommended dose. Or for your pool, use 1 lb of granular for shocking, and 2 3″ tablets for daily chlorination, replaced before they dissolve completely. You can also use poolcalculator.com – which is a great tool for chemical amounts needed, for a pool or spa of any given size.

  26. Bobbijo Dobyns

    Hello, I am new to this pool ownership, I want to make sure I’m understanding the amounts required for a 3,000 gallon pool. 1 3″chlorine tablets once a week? And 3-4 ounces of shock treatment every few weeks? Please help if I am not correct on these amounts?

    • Hi, that sounds about right. Your test kit will tell you for certain, because it’s not strictly about the number of gallons in the pool. Other factors affect the ‘chlorine demand’, such as sunlight, water temp, pool usage, amount of debris, pH level, rain, etc – all of which will consume more chlorine. Your test kit or strips will confirm if you are using the right amount, not too much and not too little…

  27. I have a 10×30 pool just set up.how much shock and clorine should I use to start?

    • Hi, use just as much as your test kit tells you… meaning, if your water tests high for chlorine, use fewer tablets. If it tests low, add another 3″ tablet. Probably just 1 or 2 tablets in a floater would be perfect. Elevating the chlorine very high, for complete sanitation and disinfection (and algae or cloudy water treatment), can be done every few weeks or as needed to maintain clear water. For your 1400 gal pool, Use 1 QT of regular household bleach (unscented), or use 3-4 ounces of dry, granular pool shock. If using granular, reseal the bag up tightly, clipped with paperclips, to prevent spills and keep out moisture and bugs. 1 lb bag of shock should shock treat the pool 4 times.

  28. Christopher

    Just wanted to ask i have a coleman 26 foot pool that has about 15’000 gallons of water how much shock would i need to keep clean as the water is already quite clear. And also if the water dose be come green how much shock would be required to bring it clear again.

    • Hi Christopher, shocking the water is generally done to disinfect or sanitize the water periodically, and specifically to deal with A-B-C, or Algae, Bacteria and Chloramines or combined chlorine levels above 0.3 ppm. For a general shocking with clean and clear water, on pools of 15-20,000 gals, use 2 lbs of shock. If you have light algae in isolated spots, this would also be a proper dose. Increase to 4 lbs, for more severe algae blooms, high chloramine levels, or if you suspect bacteria contamination.

      • Be sure the pH level is on the low end of the scale when shocking, or 7.2-ish.
      • No swimming for 12 hours, shock in the evening when the sun has gone down.
      • Keep any solar covers off the pool until chlorine level falls to normal.
      • Pre-dissolve your shock in a clean 5-gal bucket full of water, stirring to dissolve, before pouring into the pool.
      • Run the pump and brush pool immediately to help diffuse and disperse rapidly.
  29. Missouriboysmom

    How much pool shock do I use for 440 gallon pool?

    • Hi, not much! Only about 1 oz. of dry measure – should bring chlorine level up to about 15 ppm.

  30. Nichele Carroll

    Hi , how much shock should I use in my Intex 24×52×12 pool??? It has 8500 gallons of water in it?? Also how many clorine tablets should I use every day?? This pool stuff is confusing.

    • Hi – Use 1-2 tablets at at time, in a floater or chlorinator. When these dissolve in 5-7 days, replace them promptly, before they completely disappear. Tablets give you yoru daily chlorine reading which must Always be 1.0-3.0 ppm, or bacteria and algae will grow. Use enough tablets to register a proper reading of 1-3 ppm on your test strips or test kit. Use shock for A-B-C, algae, bacteria or cloudy water, or if you forget to refill the chlorinator. Use 1 lb of shock, pre-dissolved into a bucket of water, or 2 lbs if the water is in bad condition. If the water has been great, then use shock just every 2-3 weeks, just to be sure the water is sanitary. Your pH level is also very important to maintain, as is proper daily filtration.

  31. My pool is 15×33 intex vinyl pool. The water is greenish and not clear. What can I use to make the water clear, and how much pool shock should I be using?

    • Hi Becky, you probably need more filtration, 24/7 – and a bigger filter, or a better filter. The ones that come with the pool are not good. You can use regular weekly use of Clarifier, and high chlorine levels to help keep the water clear. For shocking the pool, probably 1 lb. would be fine for your size pool. Consult the product label for precise dosage, relative to your pool size, in gallons.

  32. Hi my pool is about 5,400 gallons… how much shock should I put in? Also how long after shocking should we wait to get in?

    • Hi Julia, consult the label for the most accurate advice, but most shocks will say “1 lb. treats 10,000 gallons”. But, that is really for clean/clear water. If you are trying to kill an active shock bloom, you will need more, double, triple or even 4x the base dosage. Also, it can be unsafe to store half-used bags of shock, unless you clip them closed tightly and store carefully in a plastic box. So I would use a whole bag for regular superchlorination, and for algae, use two bags (32 oz). If vinyl, predissolve in a 5-gal bucket of water before adding to pool, then brush. Wait 4-8 hours for swimming, to be sure all granules have dissolved, or again, check the label, it will give the most accurate advice on swim waiting times, which varies by chlorine product.

  33. Jessica Hall

    Hello first time owner. We have a 16×52 roughly 5,300 gallons. How much shock treatment do I need to use?

    • Hi Jessica, you should use 1 lb of shock for fairly clean and clear water. Use the entire bag, as storing half-used, open bags can be hazardous. If the pool has heavy algae, fecal contamination or a very strong smell of chlorine from chloramines, use 3 lbs. For vinyl pools, pour the granular powder into a clean bucket of water, 5-gal, and stir to dissolve, before pouring in the pool.

  34. Rachel Coffenberry

    Hello! PLZ HELP! Our 10,000 gallon pool looked like a pond this spring! ( pool cover malfunctioned)
    We heavily shocked it then was told to add flock the next week because the water is completely cloudy. We added the flocculant recirculated for 2 hours then the pump has been off for 3 days with no change and cannot see the bottom to see if anything has dropped.
    From everything I’m reading in previous comments… we need to heavily heavily shock it! How much liquid chlorine should we use? Or would you suggest shock? And if so how much? We know how to maintain it pretty well but getting it from this state has been almost impossible! Thank you in advance for any help you may provide!

    • Hi Rachel, clearing up a swampy pool takes a good pH level and about 30 ppm of chlorine, or about 3-4 lbs per 10000 gallons (or 3-4 gals 12% bleach), added all at once – then afterwards, a good filter to help remove the dead matter and ‘shock dust’. Since the floc did not help, I would turn the pump on right away, and make sure the chlorine level is high, or if near zero, go ahead and shock it again. After a day, use a Clarifier, or you can floc again with Aluminum Sulfate (aka Alum), with the pump off, and then you must be able to ‘vacuum to waste’ the following day.

  35. Tiffany Fiske

    i have a 12x30in intex. im assuming its about 1692 gallons fill line is about 2.5 feet. the app im using says to use .25cups of shock. its not even registering that i put it in. im on my 3rd round now hoping it will move it up. how much powder shock should i be using.

    • Hi Tiffany, yes 2 oz of shock should register on such a small pool, but not much, I would hit it with a full pound, 16 oz, and see how that does! For your pool, it’s best to pre-dissolve the shock into a bucket of clean water, before adding to the pool, as undissolved granules may harm the vinyl, if it sits on the floor for some time… oh, also be sure that your pH is between 7.2-7.6, chlorine is very sluggish at higher pH levels….

  36. Marisa Salas

    I have a very small above ground pool for my kids. It hold 1052 gallons of water, how much shock do I need to put in it and how often?

    • Hi Marisa, for a 1000 gallon pool, to raise the chlorine level to 2 ppm, you would use 4 ounces of regular unscented bleach, or 1/2 ounce of regular 65% Pool Shock, for regular chlorination. For a shock treatment, you would use 21 oz of bleach, or 2 ounces of pool shock. You can also maintain a regular daily chlorine level by using a small floating chlorinator and filling it with 5-7 1″ chlorine tablets once per week… which is the best way, to keep a constant and consistent level of chlorine in the pool, then every week or two, ‘shock’ the pool by raising the chlorine level to 10x normal, daily levels… be sure to also maintain a good ph level of 7.2-7.5, and test for chlorine each day before use. If the pool is not filtered, or not filtered well, consider changing the water as needed.

  37. jason kennedy

    I have a 15×42 above ground pool I am shocking it for the frist time. Water is still clear but it says to shock it ounce I week it holds 4,400 gallons of water how many packs do I use

    • Hi Jason; If you are using standard Pool Shock, in the 1 lb bags, the usual dose is 1 lb per 10,000 gallons, for clean and clear water. For light, medium or heavy algae, the dose should be increased correspondingly. In your case, 1/2 lb would be a suitable shocking. After use, fold bag over tightly, and use a strong clasp to hold the bag shut. This is very important to avoid spills, and to block out dirt, moisture and insects from a half-used bag of shock, which could be dangerous if dealt with carelessly. Be sure to predissolve the shock into a bucket of pool water, before adding to your (vinyl) pool. Shocking weekly is a bit overkill, unless there have been heavy rains or heavy use, or algae is spotted, or chlorine level (from tablets) has dropped to near zero. If the water looks great, you can cut back to twice per month.

  38. Preston Bell

    I cannot seem to keep the chlorine level up in pool. I have treated for phosphates and they are now at low level. The water is beautiful. However, my Free and Total Chlorine keep reading 0. I can add liquid chlorine and it will go up for about a day and then back to 0. PH is in balance. My CYA is around 20-30. Afraid to get it too high, as I have dealt wit that before. My pool is 18×36 fiberglass, I think about 26,000 gallons. How can I get the chlorine up and have it stay up…

    • Hi, the CYA is ok at 20-30, probably not an issue with sun degradation. Now you do need to have a method of continuous and consistent chlorination – pouring in liquid is not the best way – as it results in peaks and valleys of chlorination. I would use tablets in a chlorinator, or if you want to use liquid, use a liquid chemical pump to deliver it directly into the return pipe on a regular consistent basis. Other than that – I would suspect some contamination in the water, something that is consuming chlorine, and raising chlorine demand. Often a hard and heavy shock treatment will set things right, using 3-4 lbs of shock per 10,000 gallons, or about 10 lbs for your pool, to raise chlorine level above 30 ppm, above ‘breakpoint chlorination’ threshold, where all matter will be ‘zapped’ or oxidized.

  39. Once my pool is established, how much shock should I put in and how often. It is an in-ground pool, 18×36, approximately 36,000 gallons of water. It has a vinyl liner in it. Can I put shock directly into the skimmer?

    • Hi Mike, there are 3 or 4 good reasons to shock the pool, so if none apply to you, there may be no need to shock the pool, except for the peace of mind in knowing that the water is sanitary. Shock the pool when 1). you see visible algae getting out of control, 2). combined chlorine levels, aka chloramines, exceeds 0.3 ppm, 3). Heavy pool use, 4). Greenish color after heavy rain storms 5). suspected bacteria (animals, feces, small mudslides). Otherwise, if the water looks and tests good – you can keep the shock in the cabinet. Do NOT put shock into the skimmer, broadcast over the surface for gunite pools and predissolve in a 5-gal bucket for vinyl pools.

  40. George M

    hello I have a 21,200 gallon pool that I just opened. The water is clear I saw you mention to someone else 1 pound of shock per 10 k of water should I do the same or add less since the water is clear already

    • Yes – hi George that is correct, my general rule of thumb for shock dosage is thus:

      • CLEAN/CLEAR TO HAZY/CLOUDY WATER – 1 LB PER 10k GALS
      • GREEN/CLOUDY, CAN STILL SEE SHALLOW FLOOR – 2 LBS PER 10K
      • MEDIUM GREEN, CAN BARELY MAKE OUT BOTTOM STEPS – 3 LBS PER 10k
      • DARK GREEN, VISIBILITY OF <24″ – 4 LBS PER 10k… and so on!

      Be sure that your pH level is a suitably low 7.2 to 7.4, where chlorine is most potent!

  41. Derek Lizo

    I have a 20K gallons inground Pool , concrete,,, how much pool shock do I need ??

    • Hi Derek, if the water is basically clear or a little cloudy, go with 2 lbs, or 1lb per 10K gals. For green algae or very cloudy water, double the dose. For heavy algae triple dose, which is 3lbs per 10K gal, 6 lbs total. Or more – if the pool is basically a swamp.

  42. Nick green

    Hi I have a 32×16 above ground pool and I want to know if I should let it go green over the winter and then shock it in the spring or keep it clean through the winter

    • Hmm, good question Nick! The best choice I think would be to lower the water level, add a bottle of good algaecide and put on a tight fitting winter cover. If you are leaving it open to the elements, staining or scaling could occur, if that matters to you. Letting it go too far, could also give you trouble in the summertime with algae, unless you drained and refilled the pool in spring. You could easily kill the algae in the spring with shock, but in my view, it’s best to have water that is not so full of dissolved solids (dead algae and shock remnants), it can be easier to manage. However, you could also strike a middle ground, and use just enough chlorine, and occasional cleaning with nets and brushes, to keep the water condition from getting too bad…

  43. Richard Tourville

    We have an 18′ dia.above ground pool. 8,000 gallons. How much shock for winterizing? Also will be adding algiside.

    • Hi Richard, if the water is clean and clear, just one lb. of shock is sufficient. If using chlorine shock, wait a few days before adding the algaecide, usually added after you lower the water level. High shock chlorine levels can disrupt or destroy pool algaecides. If using non-chlorine shock, like in our Winter Kits, no worries, and they can be added in a close time-frame.

  44. Hicham Benkebil

    Hello there, I’ve had an above ground 12×30 pool for about 2 weeks now, I’ve been filtering it for 6 hours a day and using saltwater chlorinator for 4 hours a day. However I noticed some brown sticky stains on the liner, I’m assuming it’s a dead algae. I’m planning on shocking it tomorrow for the first time. What type of shock would you recommend and should I do it with the filter on and chlorination off? Your input is much appreciated, thanks!

    • Hi Hickam, yes keep the pump running and you can leave the chlorinator on too. For small vinyl pools like yours, you can shock with household bleach, or you can use granular pool shock. Your pool holds around 1700 gallons, so you may need only 1/2 bag of granular shock. For vinyl pools, it is best to pre-dissolve granular shock in a bucket of water, to prevent bleaching of the vinyl from undissolved granules sitting on the floor. If granules fall in, just brush them around until they dissolve. If using bleach, add 1 qt, or 32 oz, up to 50 oz. for your pool size. Also important for shocking is a low pH, around 7.2, where chlorine is more effective, or potent.

  45. Michelle Smith

    My 16×48 intex pool with saltwater system is lime green. Pool store says all my readings are perfect but pool is still green. Added metal free, no change. Added algaecide and now Pool is still green and cloudy. Took out filter and it’s totally brown (but it’s not debris). Put a clean filter in and started the boost cycle on saltwater system . Should I shock it with just regular chlorine instead?

    • Hi Michele, if you suspect that it is algae, yes I would add a pound of granular chlorine to the pool, and not rely on the salt system. Many salt systems have a boost or shock feature, but it’s too slow – too weak, to really perform an effective powerful shock treatment. Be sure that the pH level is on the low side before shocking (7.2-7.4)

  46. Ashley adams

    Hi! I’ve read so much and still can’t figure out my pool. It was left unattended for 5-6 years before we bought our house. Was brown and funky when we decided to open. We have shocked and put in everything the pool store has said to do. It’s now a very light green and still murky, can’t see past the second step. It’s an above ground, 24 ft rd pool, around 13,500 gallons. We’ve been using 6 bags of hypocal shock at a time, but I’m afraid it’s not enough. What should we do? Thank you!

    • Ashley, I would look at the filtration. Either it is not running long enough each day, or the filter is undersized, or the filter media is worn and needs replacing, or possibly all three. Clean and clear water is half filtration/circulation, and half sanitation/water balance. But wait… is this the same water that sat for 5-6 years? I think I would change the water!

  47. Hello, I have a oval shaped intex above ground pool. It holds 2,885 gallons of water. I was told to shock it after filling it up. I was wondering how much shock treatment should I use? Thank you and hope to hear from you soon

    • Hi Brenda, just have to do the math, if your shock treatment dosage guidelines say 1 lb. per 10,000 gallons, then you would use about 1/4 of a bag for regular superchlorination. If you need to shock for algae or other poor water conditions, you may need to use 1/2 bag, up to an entire bag for sever conditions. When using only partial bag quantities, PLEASE be careful to close the bag tightly with a chip clip or paperclip, or staples or tape, and then place inside of a box or container, to prevent spills -and- moisture and dirt contamination. Don’t mean to scare anyone, but if careless with partially used bags of shock, you could have a haz-mat situation on your hands! :-0

  48. Danielle

    How much shock do we use for a 700 gallon pool?

    • Hi Danielle, If one pound treats 10,000 gallons (consult label), then 700 gallons would use about 1/14 of a lb, or about 1.5 oz (for clear water). If the water has medium algae, double the dose, and for heavy algae, triple the dose. You can also consult poolcalculator.com for chemical dose calculations. Great resource!

  49. I got a 10 ft by 30 inches deep. 1052 gallons of water. I put a whole 1lb of shock in it.. Is that too much if so what should I do????. It’s starting to look green. I have a chlorine tablet in the pump.

    • Hi Kristal, yes that was a lot of shock for a little pool, most shocks are 1 lb per 10,000 gallons, so that’s a 10x shock level – it’s OK though, the chlorine level should come down on it’s own, in a few days or a week of sunshine. You can remove the tablet from the pump – and, tabs should be put into a chlorine floater, not the pump, where it might cause some damage when the pump is off, and the tab continues to leach.

  50. Davy, we have a 23K in-ground vinyl liner pool with a TC of 10+ and a FC of less than 1 (unreadable). I added 6 lbs of granular chlorine last week, which had no effect on the FC. Using the calculator, yesterday I added 16 lbs of non-chlorine shock, and after a day of continuous pumping the TC is 10 and FC is less than 1. Do I let the sun burn down the TC and then add granular chlorine to raise the FC, or what is the next step? The water is clear with no signs of algae. Thank you for your help.

    • Hi Tony, as you may know, when there is a difference between FC and TC, the difference is CC or combined chlorine, aka chloramines. Chloramines are chlorine combined with ammonia, nitrogen or other and it renders the chlorine useless, and causes red eyes, itchy skin and a strong chlorine smell. To get rid of CC, the pool is shocked heavily, to reach ‘breakpoint chlorination’, where everything is blasted apart, including these molecular combinations. The rule of thumb is to shock (with chlorine, not non-chlor shock, sorry…) to a level that is 10x the level of CC. So if you have nearly 10 ppm of CC, you would need to shock to 100 ppm (what?!?) – go with 30 ppm, or 9 lbs of granular shock, with a suitably low pH in the range of 7.2-7.4. Test the next day to be sure that the threshold was reached, and if so, you should see FC=TC, without any CC.

  51. Chrystal

    I have a 27×52 above ground pool. I just added water to it 2 days ago. I added 2 bags of shock and a container of ph eliminator. I also have a Frog torpedo pack. Testing it a day later I am still getting a high ph and alkalinity reading. I am not sure what to add or is it too soon to tell. Thanks for any help.

    • Hi Chrystal, for high pH and high Alkalinity, you first work at bringing down Alkalinity, to around 100 ppm. Since Alk and pH are close cousins, lowering alkalinity also lowers pH – and the same chemical is used for both – pH decreaser, or muriatic acid – lowers both alk and pH. So when lowering alk from high levels, you may have to next RAISE the pH or it gets too low… and then lower alk again, raise pH, lower alk, raise ph…. in this manner until both come into range.

  52. Hi there,
    I just purchased a 8’x30″ Intex ring pool. I also purchased a pool care start kit along with it, but I’m still not sure how to get everything at the correct levels.
    The test strips indicate:
    – low FAC (between 0 & 0.5)
    – low TCI (0.5)
    – Alk & pH seem good, but it’s hard to tell from the strips (might be slightly high?)
    – TH & CyA both look good.
    The start up kit came with
    – shock treatment granules
    – pH increaser and decreaser
    – alkalinity increaser
    When would I add shock? And how much?
    The kids have been in it for two days with pump running quite often.
    Any help or info you could provide would be greatly appreciated.
    Thanks for your time.
    Chris

    • Hi Chris, go ahead and shock the pool tonight, using 1/4 pound of shock. Be sure to seal the bag up tightly, and place in a plastic container, by itself, to prevent spills and contamination and moisture. Also, chlorinate daily with a chlorine tablet placed in a chlorine floater, use enough tablets to register a good consistent and constant reading of 1-2 ppm. Do run the pump nearly non-stop, to avoid problems. The cost of running the pump is much less than corrective measures for algae and cloudy water.

  53. Brent Cron

    Blue max shock-does it contain cyneric acid side of box says 36%other thanks

    • Hi Brent, the only type of chlorine shock that is stabilized is Dichlor shock. Cal Hypo shock is not stabilized, Di-Chlor is stabilized (contains cyanuric acid).

  54. Jessie Lynne

    Hi. I have a 14ft round 48 inch deep pool. I use the floating chlorinator with a 3inch tab. The water has recently become cloudy. Not green, just cloudy. Would adding shock to it help? If so how much do i put in? I just set up the pool about a week or so ago. So it hasnt been up for long but the kids have been in it almost everyday. Thank you!

    • Yes, shock the pool, it could be unhealthy water that could make your kids sick. Are you running the filter each day for long enough? The filters that come with small pools are not very large or effective and running it longer, even 24/7 may be needed for clear water.

  55. How much shock don’t put in an above ground 16 x 48 pool?

    • Hi Sarah, I like to use poolcalculator.com for calculating chemical amounts. 1 lb of pool shock (pre-dissolved into a 5-gal bucket), will raise your chlorine level to 15 ppm, which is a decent shock level. (I am assuming your pool is 5500 gallons)

  56. hi have a 15 ft by 36 inch pool how much of the bag of shock do i put in

    • Hi Tyler, I think your pool is around 3000 gallons. Most shock brands are 1 lb per 10,000 gallons, to reach 10 ppm – but check your label to be sure. If so, adding 1/3 lb will be sufficient to shock the pool, with clear water. If killing algae, a double shock or triple shock may be needed to fully blast the algae effectively, but for clear water, just 1/3 to 1/2 bag.

      NOTE: Please be careful with opened bags of shock, they should be folded over, and clipped tightly, then placed in a plastic box with no other chemical types, to protect from spills, moisture, dirt, bugs and other contamination, all of which could result in fire or explosion.

  57. sharon maidment

    I have a 5′ x 5′ x 1 ft deep round kiddie pool and wonder how much swim shock to use in it and also wonder if that will be okay to use on this kiddie pool. I don’t want to have to dump the water daily, I figure it is about 150 g asllons.

    • Hi Sharon, I use poolcalculator.com to figure such amounts. About 1 heaping tablespoon in the morning and another at night should keep your water clear for several days to a week, depending how much dirt and debris gets in, and how much sun it receives. Use some chlorine test strips to fine tune the amounts, to keep 2-5 ppm of chlorine in the water at all times (constant and consistent is best). Also, pre-dissolve the shock granules in a coffee mug or cup before adding, and then brush and skim the water (you can use a clean push broom if you have no pool brush), to give it some daily circulation and remove any thin biofilms from the surfaces, and leaves and debris, etc.

  58. hello, I have a 30000 plaster pool with a severe case of black algae. I have tried algaecides of different types along with shocking the pool and scrubbing with a wire brush during the process. This seems to make little or no difference to the black algae. Starting PH is about 7.2 and alkalinity is 100. Any suggestions on a better approach?

    • Hi Doug, the most permanent treatment for Black Algae is to replaster the pool, and replace the pool filter media, and purge the plumbing with chemicals. The second best treatment is drain the pool and pressure wash the heads off, followed by a bleach (12.5% liquid chlorine) washing of the pool, and 3 times over 3 days, would be even better. Some folks like to acid wash first, then rinse fully, pump out the pool, rinse again with water, and then do the chlorine wash. Then you should replace the entire filter or just replace the filter sand, cartridges or DE grids (filter media). Plug the pool pipes and fill with bleach while filling the pool. Also important to throw out any soft fabric pool floats, pool noodles, skimmer nets, pool cleaner debris bags, and swim suits, which may be contaminated.

  59. Julie Compton

    Hi I have 10ft 30 inch high pool and the free chlorine is at the top. The ph is ok how can I reduce the free Chlorine. I have taken the floater out. When you change the filter the water looks a bit cloudy. Any ideas

    • Hi julie, it will come down on it’s own – the chlorine level. Removing the tablets is good, as well as any covers or solar blankets. Brushing and skimming the pool can have a small effect, or any water agitation, such as running pool cleaners or fountains, waterfalls… Sodium Thiosulfate is a chlorine remover that we sell, but by the time you get it and put it in… in good sunlight high chlorine will normally drop into lower range in 2-4 days

  60. We have a 20×40 in-ground pool. We are having trouble getting it crystal clear this year. We need to shock it, how many gallons of liquid shock do we need?
    Thanks!

    • Hi Diane, if your pool water is fairly clear, a shocking to 10 ppm should be sufficient to clear out microcontaminants. To reach this level, 2 gals of 12.5% pool bleach or 1 gal of 5% household bleach will do it, with a suitably low pH 7.2-7.6.

  61. I’ve gotten a 10ft round x 30 inch deep for my grandkids when they are over. I know its roughly around 1000 gallons of water. How much pool shock should i be using to open it on father’s day?

    • Pat, when filling it up, there is usually no need to shock it right away. After the use is done for the day however, the water could use 2-3 oz of granular pool shock (65%), or 2-3 cups of liquid bleach (6%). Give it a good brush and skim and run the filter 12-15 hours per day, or as needed to keep the water clean. Shocking is also as needed or every few weeks. For daily chlorination, it’s best to use chlorine tablet(s) in a chlorine floater, for a consistent and constant level of chlorine. pH is also important! Keep it between 7.2-7.6 – at 8.0, only half of your chlorine is active (the rest is wa$ted).

  62. Hello! I just bought and set up a new above ground pool. It’s 12ft wide, 30 inches tall, and we calculate roughly 1700 gallons at the most. We have a filter running, and anticipate letting it run for at least 24 hours before anyone gets in, but to be honest that’s where our instructions stop. Do I need to chemically treat it? How do I do the initial treatment? We’re hopeful to have it usable by the 17th for our fathers day bbq, but I’m at a loss as when and how to get it ready.

    • Hi wendy, the best way to chlorinate a small pool is with a small chlorine floater and 3″ chlorine tablets, just one or two at a time, replaced weekly as they dissolve. Use enough tablets to maintain 1-2 ppm of chlorine (your test kit will tell you the right number of tablets to use), and keep a good pH level of between 7.2 and 7.6. High pH levels destroy chlorine. Every few weeks, or if you notice algae, cloudy water, or after heavy pool use, shock the pool with enough granular pool shock to reach 10-15 ppm. For a pool of 1700 gallons, that’s only about 1/2 lb. When using only half a bag of pool shock – be careful to seal it up tightly to block out moisture, insects, dirt and to prevent spills – very important, could be hazardous to have opened bags of shock laying around. To compute other chemical needs for any size pool, I like to use poolcalculator.com

  63. Anne Simpson

    I have a 278 gallon blow up pool, and the day after I filled it it rained and the water turned brown. I bought hth super shock and it did nothing. I only added 1/4 cup, as that’s what I figured the math to be. That was almost 3 weeks ago. I just bought some ultra blue shock that says 1 lb for 12000 gallons. Can I add it safely after the hth a few weeks ago, and how much? I read above you said 1 oz for the 420 gallon pool I think it was.

    • Hi Anne, the easier thing would be just to drain and refill – it’s not really that much water, and if it has been sitting for 3 weeks stagnant, it may have all sorts of problems, that will cost a lot more in chemicals… the 1 oz for 420 gallons was for shock that is 1 lb per 10,000 gallons, so your shock would be 20% less, or about 3/4 oz. You can use poolcalculator.com to figure out exactly how much shock or other chemicals to add to a pool of any size, that’s where I do it… 🙂

  64. Jessica Renea Ray

    Hello, I have just purchased my first 10,000 gallon pool. I see all kinds of things in the pool area and I have no idea how much shock, chlorine, and thing my pool needs. I have no idea what the Ph levels are supposed to be, or even how you check them. Someone please help me… what do I do?

    • First thing to do is to buy a test kit, and check your chlorine levels and pH levels. Add chlorine when the level drops below 1.0 ppm, and add pH increaser or decreaser if pH drops below 7.2 or above 7.8. Use chlorine tablets in a floater or chlorinator for everyday (constant and consistent) chlorination, and use pool shock for a super-chlorination treatment every few weeks, for the ABC’s – algae, bacteria and cloudy water. Run the filter 12 hours per day, or longer if the water looks hazy or goes green. And keep reading our blogs and posting more questions!

  65. Got my kids an above ground pool this summer. Everything I read on it says it’s about 420 gallons, it’s a round 6 ft diameter pool that is 30 inches tall. I’m needing to know how much shock I can put in it to get it clean.

    • Hi Diana, that’s a pretty small pool, just 1 oz. of Cal Hypo pool shock would raise the chlorine level to 10 ppm, in a 420 gallon pool. 1 cup of (unscented) household bleach would also reach 10 ppm. For daily chlorination, a single tablet in chlorine floater would be enough, maybe too much, might better use a spa chlorinator, and 1″ tablets. Tablets are best for consistent and constant chlorination, shock is used to superchlorinate the pool to clear cloudy water, algae and bacteria. You could add very small amounts of granular or liquid shock (one fifth of the amounts above), to raise the chlorine to 2.0 ppm, to prep the pool for swimming. Use a test kit or strips to manage the chlorine levels, or your pool could harbor bacteria that can cause illness. pH is also important for chlorine potency – best in the 7.2-7.4 range. If your pool water gets unmanageable this summer – the best solution may be to pump it out and refill.

  66. I have a 12ft 1700 gal pool and I would just like a simple explanation as to how much shock treatment to use and exaxtly how many chlorine tablets I should put in the flotation device

    • Hi Cassie, for tablets I would think just one at a time would be sufficient, you can adjust the baffle on the bottom for more or less release – or to control the dissolve rate. For the shock treatment, a 1 lb bag of shock is meant to treat 10000 gallons, so adding the entire bag would be needed only for a fairly severe algae bloom, or on spring start-up, but for a regular shocking, 1/2 lb should suffice. However! Half opened bags of shock can be hazardous, so fold the open bag over several times and clip the bag shut tightly, and store in a plastic bin – to be sure it doesn’t leak out or mix with other chemicals, or absorb humid air moisture into the bag.

  67. Hi This is my second year of having an above ground pool and there is sooooo much information online, I just go into a mental panic every time I try to work out what to do.
    I have a 15ft pool (33inches deep) and I’ve read online that this has both a 5000gallon AND a 3500gallon water capacity. There’s my first point of confusion.
    I just want a step by step list of what to do to keep the water good … but such a list does not seem to exist. Is there a simple routine to follow … and I mean SIMPLE!? Right now I have a slightly cloudy pool (with a fine brownish tinge) and a one-pound bag of 4-in-1 HTH super shock treatment. Can I just pour it all in?
    I have a “Flipping Frog.” in the water. Is that sufficient for the siz of pool I have? And also, which automatic vacuum cleaner would you recommend?

    • Hi Donna, let’s assume that your pool has 3500 gallons, because they are never filled to the absolutely brim.

      1. Add lb of shock to the pool, by pouring into a clean 5-gal bucket filled with water. Stir for a few minutes to dissolve. Pour into pool, and add more water to redissolve granules. Do this every 1-3 weeks to kill bacteria and germs and algae.
      2. Keep your flipping frog cartridges replaced on time. Otherwise, you can use one or two 3″ chlorine tablets to a chlorine floater, and adjust the baffle on the bottom to dissolve enough chlorine into the water (everyday) so that you can test a consistent and constant chlorine reading (with your test strips), of at least, absolute minimum 1.0 ppm, up to 3.0 ppm (normal) maximum. Use tablets for everyday chlorination (1-3 ppm) and the shock for an occasional ‘superchlorination’ of 10-15 ppm of chlorine. As water warms, the pool will need a bit more chlorine.
      3. Test the pH at least weekly, 7.2 – 7.8 is the best range. If needed, add pH increaser (when below 7.2), or add pH decreaser (when above 7.8) *important
      4. Run the filter at least 12 hours per day, and during the day, when the pool is likely to be used. Run it 24/7, if needed, when water temps warm.
      5. Add clarifier to help out the little filter, and clean the filter cartridge often, replace it 1-2x per season.

  68. Elaine Rooks

    HI! I have a 26,000 gal. 18′ x 36′ inground pool. How many 1lb. bags of shock should I use to open my pool? We just took the cover off. Could you give me the steps of what I should do first. second, etc.? I have purchased the shock, algaecide and chlorine. Thank you.

    • Hi Elaine, Step 1: balance pH and alkalinity – pH should be on the low side 7.2 to 7.4, for the shock to be most effective. Use 3 bags or 3 lbs of shock for light green, 6 lbs for medium green with low visibility (thru the water) and 9 bags if it’s dark green and you can’t see the shallow end floor – or otherwise keep adding shock until the pool turns a milky blue color. After shocking brush the pool thoroughly. Run the filter all day/night. Next day vacuum the pool and clean the pool filter, and start adding chlorine tablets – check that stabilizer level (cyanuric acid) is a minimum of 30 ppm, to conserve chlorine from UV degradation. When the water begins to clear and the chlorine level drops below 5 ppm, add the initial algaecide dose, following label instructions. Enjoy the summer!

  69. Sean Randall

    Hi There, i have a pool with 174m3 of fresh water. It is a club pool so has significant use during the summer (10 m from the sea, bathers jumping in after a sea swim). I like to run the Free Ch level between 3-5ppm. Although i have read numerous articles i am confused as to ho much Chlorine i should add to shock the pool or the ratio between Free Ch and CC. Lets say that my readings are 2.8ppm Free Ch and 3.3 Total Ch, this would make the CC 0.5. Do i need to raise the Free Ch to 10x 0.5 = 5ppm? Also, what triggers the need to Shock a pool based on the Free Ch and Combined Chlorine readings?

    • Hi, the general rule of thumb is anything over 0.3 ppm of CC is high enough to cause a problem, and warrant a good shocking. And you are correct that the general rule of thumb is to shock to reach a level of chlorine that is 10x the level of CC, so your math is correct, 5 ppm. However, to be sure that breakpoint chlorination is reached, I would use a higher multiplier of 15x and if your pool uses cyanuric acid (Stabilizer), raise it to 20x or 30x if CYA is over 50 ppm, to counteract the suppressive effect of CYA on free chlorine levels.

  70. Davy, Try to open 18k gallon in ground pool. Visible algae on bottom was vacuumed to waste. I then brushed the pool good and brought alk, ch, and ph to normal levels. Over past 2 days added a bottle of poly quat 60 in 2 doses. Lost all chlorine quickly so added 3lbs shock yesterday, this morning reading 0 ch, added 2 more bags of dichlor, as of noon reading 0 ch. Wife has now added 4 gallons of bleach. All that to ask is the polyquat having a negative effect on the chlorine? Shouldn’t that much poly have killed the algae by now? I am running pump 24 hours. If ch bag to 0 this evening should I aim for 30 ppm ch and try and keep it at that level for several days? Thanks

    • Hi Gary, no problem or interference from the Poly 60 – in fact, chlorine shock destroys the polymers, so the two should not be used within a few days of each other. You nailed it in your last sentence – yes – with a good pH level (on the low side), shock the pool to achieve 30 ppm – your test kit won’t go that high of course, so you have to do a little math first.
      – 1 lb of your basic Cal Hypo (65% available Cl) will add 8 ppm per 10,000 gallons of pool water
      – 1 lb of your basic Dichlor (56% available Cl) will add 7 ppm per 10,000 gallons of pool water
      – 1 lb of Super Shock (73% available Cl) will add 9 ppm per 10,000 gallons of pool water
      So, for 18K pool, (let’s say 20K, the math is easier!) you will need 8 lbs of Cal Hypo Shock, or 9 lbs of Dichlor shock, and you should reach 30 ppm – However! That math assumes fairly clean and clear water, if a pool has severe algae or heavy debris load, oils, mud, dead animals, etc… it will need correspondingly more shock to reach the breakpoint threshold where everything is oxidized. Add the dose all at once, with filter running and brush pool immedately afterwards. Run filter all night if possible, and if you can test a good chlorine reading after 12-18 hours, you have broken through the contaminant shield and regained control. If chlorine is near zero the next day… (missed the mark darn-it), try again with 20% more shock this time.

      • Thanks, that seems to have done the trick. Looking much better. One additional question.. I seem to have trouble filtering out the finest particles with my sand filter. Do you recommend adding D.E. to the skimmer, and or a filter sock, or another solution?

        • Hi Gary, sand filters can have trouble trapping very fine, silty dirt – it’s normal (yet annoying). A cup of DE powder can be used, or a cup of Alum (aluminum sulfate) added through the skimmer. Both form a layer on top of the sand bed and help trap more silty dirt. Backwashing flushes it out. Another solution specifically made for this issue is the Slime Bag – a filter bag that attaches to the return wall fitting, and traps very fine silt. It can be used during vacuuming, or on spring opening or algae cleanup, or it could be left on all the time if needed.

  71. I have a 25,000 gallon inground pool. Every year I cannot hit breakpoint and need an oxidizer to bring my total chlorine to 0. Then, I raise my free and total chlorine levels. Please help. This year, Pool is clear after shocking with 5lb super shock it 73, heater is off, no stabilizer or salt has been added. Here are the readings:
    Total chlorine: 7.5
    Free chlorine: 0.0
    Ph: 7.3
    Total alkalinity: 115
    Calcium hardness: 125
    Stabilizer: 0
    Salt: 2700

    Do I add more chlorine? This is the same problem every year.

    • Davy Merino

      wow – 7.5 combined chlorine is high! More chlorine yes! the general rule of thumb is to shock to reach a level that is ten times 10x greater than CC level – so that would be… 75 ppm! Roughly 25 lbs of cal hypo (65%) pool shock would be required, to reach breakpoint chlorination of 30 ppm. And you’ll need about 6 lbs of cyanuric acid, to raise the stabilizer level.

  72. I just uncovered my pool for the summer. The water is basically clear. There is a little white stuff that comes off the liner that will probably make the water milky once it is brushed down. Do I assume the pool needs to be shocked? To me, it doesn’t appear to need it. I live in South Carolina.

    • Davy Merino

      Hi Janice, always a good idea to shock the pool when the water has been stagnant for long periods of time. Algae is visible, but bacteria is invisible, so even though it’s clear, it may not be healthy or sanitary.

  73. Hello,
    I have a 30,000 gallon in ground pool. We bought the home at the end of summer last year and the pool was not maintained. We had it winterized for the winter and it does NOT have a cover. So you can imagine how gross it looks. We are replacing the vinyl liner this spring. We think there is a line leak somewhere and have to have it looked at. What is the best way to clean out all the YUK and somewhat clear the water? I’m afraid if I drain the pool the pool side may cave in.

    • Davy Merino

      Hi, the best way to clean out the yuck is with a ‘trash pump’, which can be rented with suction and discharge hose. If you are getting a new liner in a few months, I wouldn’t worry about cleaning the pool now, just pump it out when ready to measure the pool for the new liner. 99.9% of pools can be drained without any worry about the walls. Vinyl liners will shrink slightly or may not set properly again when refilled and for this reason, vinyl pools are discouraged from draining completely, unless a new liner is being installed.

  74. Bob Morgan

    we are trying Cal-hypo in our 250 gal. spa and wondered how much we should add to begin with? we tried the bleach method and it irritated our eyes and sinuses, so we drained the spa and refilled with fresh water bought a Mineral Sanitizer (yellow) for the cal-hypo. Is there anything we should be informed about or check for. this is our first spa and we are having some water issues that is why we are going this way.

    • Davy Merino

      Hi Bob, with the Nature2 spa stick, you could just use non-chlorine shock once or twice per week, and use chlorine shock once or twice per month. For Cal Hypo shock, you need less than 1/2 oz. to raise the chlorine level in a 250 gal spa. Use the type for spas, in a bottle, not the type for pools, in a bag. Bleach can also be used, but you may have overdosed it. Just 5 oz. of 6% bleach would shock a spa your size really well, to about 10 ppm.

  75. I have a 16′ x 32′ oval pool that I think is around 20,000 gallons. It hasn’t been operated since Oct last year. I want to clean it up as it is green before closing it. How much shock do I need to get?

    • Davy Merino

      Much better if you can drain and clean the pool. Even if it’s vinyl, you have to get the sludge out. And even if you kill all the muck and yuck, and eventually restore the water, the remaining matter in the water could give algae problems in the future. Even if you can only drain half the pool, I would advise that, to start. If the pool has been covered until now, with only minimal debris, you could try to bring it back (without draining any water) with good chemistry, lots of shock, constant filtering, and even then it could take weeks, if you are lucky. So consider replacing some of the water first.

      OK moving on, start with good pH and alkalinity levels as the first step. Most important is a stable consistent pH level on the low end of the scale, or even temporarily below 7.0, into the acidic range. Chlorine is Much more effective at a lower pH level. In a pool full of algae, the pH is usually very high, and the alkalinity may be high too – both can resist your changes to pH, you may have to treat with pH decreaser several times per day, until the pH stabilizes and stays low, between 6.8-7.2. Be sure you have a solid and consistent pH level.

      Next, be sure the filter is operating very properly and effectively, and all systems are ready to go, for near 24/7 filtering for several days or weeks. If the filter sand, cartridge or grids look old or have problems, it will slow down the process.

      Finally, shock the *&$%# out of the pool, with a LOT of shock. Probably about 5 lbs, per 10,000 gallons, more or less, depending on visibility and amount of solids. keep adding until the water turns blu-ish, a cloudy gray color, with no hint of green. Shock at night, or after the sun goes down – the next morning, there should be a testable chlorine reading, or chlorine remaining in the water. If the chlorine level is zero “0” – shock again, because the chlorine demand is still higher than the amount originally used.

      Brush the pool, everyday, twice daily. Add clarifier and then algaecide over the following days. Be vigilant with ph, chlorine level and filtering, and it should come back.

  76. Regina Miller

    I have a 36 x 54 round above ground pool that is totally green with algea. I’ve tried everything, algea, shock, metal out. The pool co.said to put in 15 pounds of shock. Will this damaged my liner or clear up my pool? Sounds like a lot of shock. Should I just pour powder in pool or pre dissolve even though it says not to pre dissolve. I don’t want to damage my liner. Been battling this for a month.

    • Davy Merino

      Hi, it does sound like a lot of chlorine, but it depends on how bad the algae is, if you can’t even see the bottom, it could be the right amount. You need at least enough to kill all the algae, and 15 lbs may be the right amount, give or take a few lbs. I would pre-dissolve the shock, unless it’s Lithium hypo pool shock or non-chlorine pool shock. any other type of granular could possibly weaken the liner, or bleach a liner. In your case, the thick green coating will protect the liner somewhat, lol – and shocking a pool once doesn’t usually bleach a liner, but doing it very heavily or repeatedly, without brushing the pool afterwards and running the filter, could damage the liner. So if it was me, I would predissolve, 3 bags at a time, into 4 gallons of pool water, pour it in the pool, and repeat 4 more times. Get a helper that can brush the pool constantly, during the process – and be sure your pH is on the low side first, 7.2-ish, for greatest chlorine potency.

  77. Adrienne Miyaji

    I have a 10’×30″ above ground pool, which hold about 961 gallons of water, how much shock treatment do i need to use?

    • Davy Merino

      Hi Adrienne, Not Much! For a 1000 gallon pool, you need very little, well – depending on the condition of the water.
      Clear-blue: 12 oz of 5% bleach or 1.5 oz of cal hypo 65% shock.
      Hazy, Dirty: 24 oz of 5% bleach or 3 oz of cal hypo 65% shock.
      Green Algae: 36 oz of 5% bleach or 5 oz of cal hypo 65% shock.
      If using Cal Hypo shock, measure out using a 1/4 cup scoop (2 oz) and predissolve in a clean bucket of water before adding to the pool. Then be sure to seal the bag tightly with paper clips and store indoors after opening, out of reach of children.

  78. Pat Sauer

    Getting prepared for hurricane Irma and will have to evacuate soon.
    Have a 10,000-gallon in-ground pool and preparedness folks say to really shock the pool because power will go off at some point and possibly for quite some time.
    Pool chemical levels are balanced right now(free chlorine, ph, hardness, stabilizer, etc.), so how much liquid chlorine should I add to the pool for hurricane preps? I just added 2-1/2 gallons–should I add more and if so, how much?

    • Davy Merino

      Hi Pat, I think you are good with 2.5 gallons. Your chlorine level should be about 12-13. Keep the filter running until the power goes out, or until you have to evacuate. Just before leaving, test the water, and if it’s down into normal ranges, hit it again. Each gallon (of 5% bleach) should give you 5 ppm, per 10000 gallons of pool water. You could go as high as 25 or 30 ppm, but I wouldn’t go higher than that (5 or 6 gallons). If you were using granular shock, the equal amount would be 5 or 6 lbs. Good Luck!

      • Pat Sauer

        Okay, made it through Irma and pool looks pretty good. Power only out 2 days. Glad I heavily shocked it.
        I have another question: Since I know nothing about pool chemistry, if a friend said she buys large bags (5 pounds) of baking soda for a friend’s pool, what does the baking soda do and would it replace a pool-store-bought chemical and do the same thing? I assume baking soda is less expensive than the pool store equivalent chemical?

        • Davy Merino

          Hi Pat, Baking Soda or Sodium Bicarbonate or Bicarbonate of Soda, can be used to replace Alkalinity Increaser, which is also baking soda (not to be confused with baking powder(!) – does the same thing, yes – to increase Total Alkalinity. Should be less expensive than ‘pool grade’ bicarb.

  79. I have a 5000 gallon summer waves pool we have well water which left the pool with brown Rusty water we got the rust out of the pool which the water changed color now it’s like a greenish blue color what would be my next step into getting the pool clearer??? Maybe shocking it or liquid chlorine?

    • Davy Merino

      Hi Kai, Shocking heavily has the usual effect of knocking minerals out of solution, so they become visible floating in the water, or they immediately deposit themselves as stains. Don’t shock, unless you suspect the green color is actually algae. Test to be sure you have constant 1-3 ppm of chlorine, with a suitable pH level of 7.2-7.6. Calcium, Cyanuric and Total Alkalinity levels should also be balanced and good. Then – you treat with a sequestering agent, to bind the minerals, locking them chemically into solution, so they become invisible again, and can’t stain surfaces. Use Stain Away or Metal Free, or any good “Stain & Scale’ product. Add initial dose, then follow maintenance dosage guidelines, because the chemical degrades in 1-2 weeks, and needs to be reapplied. Your pool filter may need replacement, the cartridge may be bad, if it has stains and needs cleaning often. Also – next time you fill the pool, and for make-up water, consider using a Pre-Filter on the hose, to remove metals and minerals.

  80. Have a 30k gallon pool that recently became overrun with algae when we were on vacation. We have monitored levels and dumped a huge amount of shock over the last week with absolutely no improvement. The pool is dark green but FC levels are optimal. We just installed a Jacuzzi cartridge filter system last month and it was working incredible until now. Do you think the filter system has something to do with being unable to get any kind of improvement? We have taken cartridges out and cleaned them twice. Please advise.

    • Davy Merino

      Hi, it could be the filter, yes. Make sure that all internal parts are in place, to force the water thru the cartidges. Loose or missing parts can cause water to bypass the grids. Secondly, start running the filter 24/7, if you aren’t already. Third, make sure your pH level is low, around 7.2, for greatest chlorine potency. Dark green you say? Needs more chlorine – much more (and a low pH), until the water turns a blue – gray color. If still not turning around, I would suspect Phosphate contamination, which can be tested for with phosphate test strips, and treated with phosphate remover.

  81. Hi, I have a 10,000 gallon in-ground pool with pebble tech plaster and the color is called “French Grey”. Normally, in direct sunlight, the pool looks very blue and refreshing. Here lately though, I could swear the pool is looking somewhat of a minty green… especially in the deep end. That being said, the water is CRYSTAL clear. I can see something on the bottom of the pool in the deep end with absolute clarity. So my question is…am I just nutty and seeing things, or is it possible to have an algae problem without ANY signs of cloudy water?

    • Davy Merino

      Hi Brent, it could be metals or minerals causing the color, or pollen. Especially since you see it more in the deep end, you’re not nutty. Try using a Stain & Scale sequestering agent to lock up minerals and metals, which requires maintenance doses every few weeks, as chlorine breaks it down. Now, it could also be algae beginning to form, which can be removed by shocking the pool, but since the water is clear, it is likely metals.

  82. Steve Cottrell

    I’ve got a 36,000 gallon saltwater pool. The deep end has a light green tint to it. The shallow ends look crystal clear. Walls feel a little slimy but have felt that way since pool was installed (approx. 3 weeks ago). I’ve got a DE filter along with a chlorinator. What is the proper procedure to shock and treat?

    500ppm hardness
    Total chlorine/bromine 0
    Free chlorine 0
    pH 7.6
    Total Alkalinty 240
    Cyaniric Acid 30-50

    How much pool shock would you use to get rid of green tint (I assume algae just starting). Thanks in advance!

    • Davy Merino

      Hi Steve, I would use 4 lbs of granular pool shock (Cal Hypo), for a pool in your condition (act fast). Check chlorine level 8 hours later or in the morning, and you should still test a high level. If it is zero 8 hrs later, you may need to shock again, with a heavier dose, to kill whatever is consuming the chlorine. shock works best at a low pH level, so if possible, lower pH to 7.2 before shocking, although your very high alkalinity level may resist changes to the pH. Liquid Acid or Dry Acid is used to lower both pH and alkalinity, so treat your alkalinity first, to lower below 150 ppm, by adding acid, repeatedly as needed, until alkalinity comes into range. Your pH level may go too low however, during alkalinity reduction, so you may have to add pH increaser, in between alkalinity treatments, to keep pH above 7.0.

      Shocking the pool adds chlorine to the pool just like tablets or your saltwater generator, the same hypochlorous acid, but it does it fast and all of a sudden, raising chlorine levels very high to kill algae, bacteria, and break apart contaminants and chloramines. It can also be used (granular chlorine) to maintain chlorine levels during equipment problems. And although many salt systems have a ‘shock pool’ feature, many owners don’t want to stress out the salt cell too much, plus it’s still much slower than pouring in chlorine powder, or using non-chlorine shock (useful for contaminants and chloramines, but not a disinfectant). Saltwater pool owners may use pool shock during pool opening and closing, or 1-2x per month to oxidize and sanitize the water, to reduce the work load for the salt cell, and to reduce chloramines, or treat for algae or cloudy water.

  83. Starting pool up from sitting over winter/spring (new chore for me). Size is aprx.11750 gallons ph, alk, both very low. from reading am adding around 7 lbs. sodium bicarb to raise alk and hopfully ph. after application how long do I wait before shocking pool and how much shock do I use for my pool size?
    Thank you.

    • Davy Merino

      Hi Beverly, only an hour or so, then recheck chemistry. For best potency from shock chlorine, a low 7.2-ish pH is best, so if it’s still a bit low that’s oK, you can adjust up to 7.4-7.6 after shocking. For your pool size, I would use 2 lbs of pool shock for hazy water, and 3-6 lbs if green, less if you can see the floor, more if not. If dark green, keep adding until water turns blue/gray color, with no hint of green, then brush and filter, then vacuum to waste.

  84. Christel

    30,000 gallon inground pool. Currently growing algae on textured walls. I am just starting the big shocking process to kill the algae while brushing. I am currently using bleach for chlorine to kill. How many gallons of bleach per hour should I add for this size pool? Thanks in advance.

    • If the algae bloom is small, 10 ppm should kill it. If the entire pool is green, go for 20 ppm, and if it’s dark green with low visibility of 12-24″, shoot for 30 ppm. For regular store brand household bleach of 6% strength, and based on poolcalculator.com – 10 ppm would be 622 oz, or double or triple the dose, to reach 20 or 30 ppm. Divide total amount by 128 oz (in each gallon).

  85. my pool is 26 around and I was wondering how much shock it I need to put in if I have green water?

    • Hi, just enough until it turns a blue/grey color, without any hint of green. Your pool has about 12000 gallons, so I would start with 4 lbs of pool shock (pre-dissolved in a bucket of water). If it still looks green-ish, add a little more. Be sure the pH is on the low side, 7.2-ish, before shocking. Add shock in the evening. Check pH and chlorine the next morning, and if the chlorine is zero (0), and the water looks greenish again, then hit it hard again.

  86. Lupe ferreyra

    Hello i have a 16×48 inch pool. I just set it up yesterday and was wondering about the cleaning process. I bought super shock and chroline tablets. How much of each am i supposed to put and how often? Also how long do i wait to let my kids go in after the process?

    • Davy Merino

      Hi Lupe, Use 2 tablets in a chlorine floater, or enough to produce a consistent and constant 1-2 ppm of chlorine, as tested by your kit or strips. Replace them before they dissolve completely, which will be every 5-7 days probably. Use the shock chlorine once per week or twice per month, to super chlorinate, to kill anything that the tablets did not kill. Also can use the shock if the water gets cloudy,or if you see algae, or if you forget to fill the floater and the chlorine drops to zero. Always pre-dissolve the shock into a bucket of water before pouring into the pool. Check the label for wait time, but I would wait at least 4 hours. Also check and maintain the pH level in the 7.2-7.8 range, using pH adjustment chemicals if it drifts outside of this range. Your pool may also do well with regular additions of algaecide and clarifier. Finally, run your pump more than you think you need to – 12-24 hours per day, your filter is likely very small, and needs to run often, especially when it’s hot.

  87. Rojelio Obispo

    How long should one wait before opening the pool after a shock treatment?

    • Davy Merino

      Hi, When using granular chlorine pool shock, there is generally a waiting period, consult the label for specific time. The main concern that undissolved granules can get in your eyes or ears or nose, or get stuck between your suit and skin and cause irritation. Some pool shocks like Lithium or Non-Chlorine shock are specifically “No-wait, swim immediately”, but Cal Hypo or Dichlor shock will instruct you to wait a certain period of time. If you really want to swim after shocking, a quick dip wouldn’t hurt, just keep heads above water, and don’t use a suit you like, which could become a bit faded.

  88. Lizzy Liz

    Okay so I have a 3,512 gal above ground pool and I poured half a bag of shock in my pool but I didn’t stir into a bucket, I just poured in my pool from the bag ? Is that bad ?? What should I do

    • Davy Merino

      Hi Lizzy, it’s okay – doing that once or twice per year won’t have much effect. The concern with vinyl pools is that undissolved shock granules can bleach the vinyl, or rob the vinyl of plasticizers and resins, or even burn through a very thin spot. However, this normally does not come from one careless mistake, it takes years of regular abuse, in most cases, to damage the vinyl. What concerns me more, is how you are storing your half empty bags of shock – please be careful to close them up very tightly with two paperclips, or a large chip clip, and then keep inside of a sealed container. Moisture, dirt, insects that get inside can cause hazards, or if granules spill from a loosely open bag, that could cause other calamity. Please be safe, store opened bags of shock very carefully, closed, clean and dry.

  89. Julie candow

    Water is brown how much shock for 22×52

    • Davy Merino

      Hi Julie, brown water could be from metals, or silty dirt, or oaky leaf tannins. In most cases it will shock out of the water well. After balancing the pH to the low side, 7.2-ish, add enough shock to turn the pool a blue/grey color, with no hints of brown. Could take 2 lbs, or could take 4 lbs, add 1 lb at a time until the change is observed. Then add another pound to be sure. Run the filter all night and tomorrow you can add a clarifier if needed to help the filter.

  90. Hi i have a 3,300 gallon 14×42 pop up pool and i i just set it up but dont know how much shock to put at the beginning and when its green or when needed? Help please!!!

    • HI Maribel, Check the label on the shock, most will say to use 1 lb. per 10000 gallons of pool water. For your pool 1/3 lb will be a normal shock, used with fairly clear water conditions. For very hazy water, double the dose, for visible algae, triple the dose, to an entire pound, or the whole bag. Pre-dissolve first, by pouring into a 5-gal bucket pre-filled with water, and stir with a stick to dissolve. Add more water at the end, to dissolve remaining granules, and let sit for an hour, then pour the rest in the pool. Before using shock, make sure your pH is on the low side, 7.2-7.4 range. If using only a partial bag of shock, please be careful and close the bag up tightly, and clip with a chip clip or paper clip, to lock out moisture, dirt and insects, which could cause a reaction and possibly ignite or explode (really!). Keeping open, half-bags of shock laying around can be dangerous.

      • Samantha

        This is the exact dimensions of my pool as well, my question is, do you recommend having a chlorine tablet floater in there as well, after the shock? if so i have already purchased 3inch tablets, will they work? I am just now setting up a new pool. thanks for your help!

        • Davy Merino

          Hi Samantha, yes you need both. Shock is only for regular oxidation, or to kill algae, remove chloramines or correct other water conditions – but, you must have a daily chlorine method as well. Tablets are used to provide a constant and consistent 1.0-3.0 ppm level of chlorine in the pool. Add enough tablets to the floater, so that your testing results in a consistent 1-3 ppm, usually 2-3 tablets per 10000 gallons. When they dissolve, replace them promptly, so chlorine never goes to zero (never ever!). Use shock every few weeks to kill everything that the tablets miss, or after large parties, or for algae, or if you forget to refill the floater 😉

  91. I am new to this whole pool this. I have a 15,000 gallon pool that I have spent $300 on this week and it keeps getting worse. I put 4lbs of shock in it last night and it doesn’t even look like I put any. What can I do?

    • Hi Kayla, sorry to hear of your struggles. It can be confusing, this path to clear water, but you’ll get there!

      First thing is good water balance, proper pH, alkalinity, and calcium hardness and cyanuric acid (stabilizer levels). They should be 7.2-7.6, 80-120 ppm, 200-400 ppm and 20-50 ppm, respectively.

      Second thing is good filtration, if your filter is undersized or underperforming, it can really hamper algae clean-up efforts. Consider changing the sand or cartridge, or using a filter cleaner product to restore better filtration. And, be sure that filtration is occuring (you should be needing to clean the filter, or backwash). Missing internal parts or valve issues or other problems can cause water to bypass the filter media.

      Third thing is good circulation, at this stage you should run the filter nearly 24 hours per day, brushing and skimming daily, and running a pool cleaner if you have one, anything to help increase and improve circulation. Many people don’t run the filter long enough each day, and it’s a big part of the problem.

      Finally, heavy dose of chlorine – 4 lbs of shock for a 15000 gallon pool is a healthy dose, but if the chlorine reads 0 the following morning, that means that the chlorine demand was higher than the supply – it just ‘ate it up’. Making sure your pH is on the low side 7.2-ish, shock again in the evening, with 3-4 lbs of shock, brush and run the filter all night. In the morning you should have a chlorine reading. (if not, repeat)

      So, clear water is not just shock, but filtration and circulation is also very important. Keep at it, and let me know if you have other questions! And, keep reading the blog, we have lots of good information on water chemistry, algae killing, and other fun stuff!

  92. Joe Hogg

    How much shock should I use for an above ground 1,025 gallon vinyl pool

    • Hi Joe, a normal shock is 1 lb per 10,000 gallons, so for your pool about 1/10 of a pound – but in the presence of algae or colored or cloudy water, a 3x or 4x shock dosage is not unusual. If your water is clear, I would use 1/4 cup, or 4 oz of shock (1/4 bag). If there is algae or cloudy water, use 1/2 cup or 1/2 bag, or more if needed. Pre-dissolve by pouring into a 5 gal bucket of water, and stirring to dissolve, then pour around the pool edge. Be very careful with half used bags of shock. Roll the bag down tightly and clip with a ‘Chip Clip’ or large paperclip, to keep granules from spilling, and to lock out moisture, insects and dirt, which could cause a reaction, possibly igniting or creating noxious gases.

  93. Michelle

    I have A 10 ft by 31 inches 1000 gallon how much shock do I need ?

    • Hi Michelle, a normal shock is 1 lb per 10,000 gallons, but in the presence of algae or colored or cloudy water, a 3x or 4x shock dosage is not unusual. If your water is clear, I would use 1/4 cup, or 4 oz of shock (1/4 bag). If there is algae or cloudy water, use 1/2 cup or 1/2 bag, or more if needed. Pre-dissolve by pouring into a 5 gal bucket of water, and stirring to dissolve, then pour around the pool edge. Be very careful with half used bags of shock. Roll the bag down tightly and clip with a ‘Chip Clip’ or large paperclip, to keep granules from spilling, and to lock out moisture, insects and dirt, which could cause a reaction, possibly igniting or creating noxious gases.

  94. Danielle Ney

    I have an 800 gallon pool…I added 2 chlorine tablets to the filter a few days again & another 2 today. The water is slightly cloudy, what do I need to do? If shock is to be used, how much & any other chemicals?

    • Hi Danielle, for clear water, you need good filtration, in addition to good water chemisty, meaning a good pH level 7.2-7.6, and a constant chlorine residual. For shocking such a small pool, bleach is safer to use than the granular shock normally used. Just a cup or two of regular unscented bleach, every week or two, or as needed.

  95. We have a 16,000 gal. Fiberglass inground pool. During the Winter, very high winds blew snow that picked up a tremendous amount of dirt onto our pool cover. We opened the pool yesterday, 6/8 and the water was literally brown. Put 3 bags of In The Swim pool shock in it, today is is green and we can see the cleaner if it is not on the bottom. My question is how much shock can we use and what else can we do. The cleaner bag doesn’t seem to have much yuck in it now & we have hosed the cartridge filters as good as we can twice. Any help would be appreciated. Thanks

    • Hi Beth, if the pool was still green after 3 bags of shock, that just means that you need more shock! add until the water turns a blue/grey color, with no hint of green and – the chlorine level is still high 12 hours later. First check alkalinity and pH levels and adjust pH down to around 7.2-ish. For killing algae, you need 30 ppm of sustained free chlorine, plus good filtration and circulation. Depending on water chemistry, and and the amount of algae, it can take a lot of shock sometimes. Using 4-5 lbs of shock per 10000 gals is not uncommon in my experience, and I’ve used much more at times. An alternative could be to drain and refill 1/3 to 1/2 of the pool water, which will reduce the chlorine demand by the same amount.

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