Spa Shock: How to Shock a Spa or Hot Tub

how to shock a spa or hot tub

No matter what type of hot tub and spa you own, the proper chemical balance is essential for keeping water clean and safe. For that to happen, one thing must occur: you have to shock the water. Delve into the importance of implementing routine shock treatments, explore various available chemicals, and learn about the safest methods you can practice when you’re shocking a hot tub or spa.

What is Spa Shock Treatment?

In essence, shocking your hot tub or spa means adding a higher than usual dose of oxidizer chemicals to the water. This is also known as oxidizing. Oxidation is the process of a particle losing electrons when it encounters a disinfectant. You can carry out a hot tub/spa shock in many ways. There are chemicals designed for this and information on how to use them, such as; the amounts to use, how many gallons to use, the product to choose, brand/manufacturer, effectiveness, the correct level of chemical balance, etc.

Reasons for Shocking a Spa or Hot Tub

4 reasons for shocking a hot tub

There are only four valid reasons for shocking your spa or hot tub. It’s not necessary to shock the spa every time you use it and maybe not even weekly. Shock your spa for the following reasons.

  1. To remove bromamines or chloramines in the spa. Using a DPD test kit, you can test for the level of combined chlorine or bromine. Adding an oxidizer in an amount equal to 10x the level of combined sanitizer will break apart these bonds and make sanitation more efficient.
  2. To remove organic contaminants in the spa. When 3 or 4 users jump into a hot spa, the level of contaminants spikes to a level many times higher than your sanitizer can manage. Add an oxidizer after spa use to restore sanitary spa water, by breaking down bather waste.
  3. To reactivate bromides in your spa water. For a bromine spa, using an oxidizer weekly helps maintain the bromine level in your spa water. Activating bromide ions with spa shock converts them to hypobromous acid, the killing form of bromine. More on building a Bromine Bank here.
  4. To kill bacteria. Remember that non-chlorine shock is not classified as a disinfectant like chlorine or bromine, but is useful only as an oxidizer. Use chlorine spa shock to kill bacteria or algae. You may see it, or just suspect it, or you may find the chlorine or bromine level has fallen to zero; shock to raise levels fast.

Preparing to Shock a Spa or Hot Tub

The most important thing to do in preparation for shocking the spa water is to first test and adjust the pH level to the range of 7.2-7.6. Oxidizers work best in a low pH environment, and the efficacy of your spa shock is twice as great at a pH of 7.5 than it is at a pH of 8.0. Check to be sure that your pH is not too high before shocking.

The second most important thing is to remove your spa cover, spa blanket and spa users before shocking the hot tub. Especially during the first 20 minutes, your spa surface needs to be aerated to facilitate the exchange of electrons and gassing off of byproducts formed during oxidation. Spa cover materials and components can be damaged by the off-gassing chemicals.

The third most important thing is calm water. Don’t turn on the blower but do run the circulation pump when you shock the spa. Too much agitation can prematurely gas off potent oxidants. If you notice undissolved granules on the bottom, however, you can use a brush or net to stir them around, but don’t vacuum them up.

So to summarize, when preparing to shock a hot tub:

  1. Lower pH level to between 7.2-7.6 before shocking
  2. Remove spa cover, spa blanket and spa users
  3. Calm water, keep jets on low and blower off

Shocking a Spa or Hot Tub

shock a spa or hot tub

When shocking your hot tub, pay attention to a few things. Specifically, be cautious when using spa shock, oxidizers can be dangerous when misused or mishandled.

  1. Read the label. Different oxidizers have varying strengths. Be careful not to overdose or underdose your spa shock treatment.
  2. Measure your spa shock. Dosing is so important. If you are 1/2 of an ounce off, you can underdose or overdose your spa.
  3. Add carefully. High winds can blow spa shock right in your face. Gently pour it over the surface and wash away any spills right away. Keep out of the reach of children.

Shock Before or After Using the Spa?

I know people who do it before or after, and some who shock both before, and after using the spa. If you are confident of the water balance and condition before use, there may be no need to shock before using the spa.

On the other hand, if your spa water turns dull and cloudy after use, or after use your sanitizer level is zero, and pH is pummeled, you may want to preemptively shock to boost levels. This is helpful for small spa filters that are overwhelmed with several spa users.

How long to wait after shocking a spa, before you can get in? Consult your label, but most spa oxidizers need just 5 minutes to fully dissolve, disperse, and complete oxidation.

Which Spa Shock is Best?

leisure time spa 56

We have a large variety of spa shock that can be used for oxidation. Choose one you like and get on with it!

You can use chlorinated spa shock like Spa 56 or you can use non-chlorine shocks like SeaKlear Spa Pods, or Leisure Time Renew, tabs or granular.

Remember to use an oxidizer specifically labeled for use with spas and hot tubs. Do not use pool shock in your spa. It is easy to overdose, and may contain other chemicals not needed in a spa or hot tub. The 1 lb. bags are a safety hazard if not used all at once, and react with moisture, bugs, or debris. They also spill easily, if not carefully resealed.

The most economical shock? Our own Spa Care Spa Shock. Most value, pound per pound, and just as potent. And you can use the spa almost immediately.

82 thoughts on “Spa Shock: How to Shock a Spa or Hot Tub

  1. Martin Cross

    When I checked the water chemistry an hour or so after my weekly-ish shock treatment, I noticed small amounts of very tiny white things (flakes maybe?) floating in the water. Because I have a huge fear of pipe mold (due to a horrible case years ago in my last tub) I immediately feared the worse even though this stuff was VERY tiny and planned to do a deep cleaning today. Before I started the clean I decided to do the bleach test to make sure it wasn’t calcium even though the water here is very soft and if anything I struggle to keep the hardness up in my water. When I went to pull a sample, I realized the tiny white flakes were gone. It seems like I read something over the years that shocking can sometimes cause solids to form that can be filtered during a full cycle. Did I imagine this? Should I still do a heavy shock, drain and cleaning?

    My tub is only a year old, a Marquis “Vegas” using Bromine and an ozinator.

    Thanks in advance for your input!

    Martin

    • Hi Martin, not to worry, sounds like that was what I call ‘shock dust’, and it eventually dissolved.

  2. Robert Billinghurst

    Hi
    Just got a new hot tub this week, I am using bromine to sanitise. The instructions said to to an initial shock Treatment with Bromine (three teaspoons into a 900 Litre Pool then add 1 1/2 teaspoons weekly.
    I did the initial shock and The water turned cloudy after 3 days and the Bromine level dropped to Zero (since topped up). It has been used everyday by two adults and two children. I have a non chlorine shock which I have not used yet. I am unsure as to when to add Bromine & when to shock. I have drained the pool and will start again. Any advice would be much appreciated!
    Thanks
    Rob

    • Hi Robert, it’s important to have a constant level of bromine in the water, in the 3-5 ppm range, and to run the circulation pump near constant. In addition, a good, low pH level of 7.2-7.4 range will help bromine to remain potent. The shock is useful after using the spa, to zap any particles we leave behind. cloudy water usually indicates either a lack of sanitizer, or filtration, or poor water balance, or some combination of those. Good Luck – you’ll catch on! Draining is easy enough, when you get into trouble, but will then need to rebuild the ‘bromine bank’ again with an ounce or two of bromide booster, and then continue with bromine tablets, about 5-7 tabs per week, replaced on schedule, as they deplete/dissolve. See our other spa posts in the Spa category, or by using our search box.

  3. Hi, thanks for the information–very helpful! I’m rather new to hot tubs. I’m following the guidance you outlined, but I’m still encountering unclean water and brown scum after just one use with two people in a 180 galloon hot tub. I use dichlor chlorine for sanitizer. Start with a chlorine level of 3 and then shock it with roughly 1 once of an oxidizer product called “Fresh and Clear” by Leslie Pools . (It’s Potassium Peroxymonosulfate 38%–0ther ingredients unknown). I’m told by the local pool company to add about an ounce after each time I use the pool. The next day, when I turn on the jets, I find grimy bubbles with brown scum forming and a strong odor. The only other thing in the water is a product called Spa Perfect. Other owners of our hot tub don’t seem to be detailing similar issues, so I can’t figure out what is going on. The local pool company can’t explain the brown scum to me. Should I use more chlorine or shock it more? I’m leaving it air out after each use as you suggested. Any advice would be appreciated. Thanks.

    • Hi Jim, brown scum could be a form of biofilm, which can build up in the pipes. Try Spa Purge by Natural Chemistry or Jet Clean by Leisure Time to strip out the pipes, and then drain and clean the spa.

  4. Hi,
    I am using Leisure Time spa Defender on a weekly basis and an oxidizer on a weekly basis.
    My question is, can I add them to the hot tub at the same time or do I need to add separately, add on different days, etc?
    Thanks for your help.

    • Hi Greg, with those two chemicals, I would add separately, 3-4 days apart if possible. Shock on Saturday and Defender on Wednesday, for example. High shock levels can disrupt sequestering agents like Defender.

  5. Brian Marks

    Hi, I just added spa shock. I must have put too much in, because the spa turned lima bean green instantly. 😐

    • Hi Brian, check the label for dose, you may have overdosed. If copper levels are very high, that could be causing a bright green color too. If chlorine is very high, too high – you can drain half (or more) and refill, or use our chlorine reducer chemical.

  6. Cindy Colbert

    So confused … many places say do NOT use chlorine with a bromine hot tub, others say do use it to shock. Please help me understand when/why I should NOT use chlorine with bromine? Is it simply meaning don’t use both at the same time or what. We just purchased a new home with 30000 gal in ground pool & 400 gal hot tub this summer (hot spring vanguard). The prior owners used Leisure time Reserve & Renew raving about how easy it was, etc … but I’m having to add renew every single day (getting quite costly) because the bromine levels test below 1 within 12-14 hours of adding the correct amount and this is even after the renew shock takes the levels up to 16+. Ugh. Do I need to use chlorine to shock instead? Isn’t the chlorine non-compatible with Leisure Time Reserve?

    • Hi Cindy, bromine tablets do contain about 25% chlorine by weight, in the BDCMH formula, and chlorine can be used to reactivate bromide ions into bromine, so you can definitely use granular chlorine in a bromine tub, just don’t use pool chlorine tablets in a spa/hot tub. Reserve is the bromide solution that is added just once usually, after refilling the hot tub, to build the ‘bromine bank’, and then chlorine or non-chlorine shock is used to reactivate the bromide ions into bromine. Renew is a non-chlorine shock, that is used to reactivate the bromides, but chlorine can be used – any oxidizer or ‘shock’ will do it… thanks, good question!

  7. Hello. The suggested “In The Swim Chlorine-Free Pool Shock” weekly maintenance is 1 lb per 10,000 gallons. For my 250 gal hot tub, what does that break down to? I’m guessing around 2 ounces per weekly dose.

    • Hi Mike, actually it’s closer to 0.5 oz. Or about a Tablespoon, lol. Be sure to seal bag tightly, with several paper clips and place inside a tupperware, to keep out moisture.

  8. You still have not clarified the question about shocking the spa..break it down.. 1st you have ro establish bromine..How? Then you have to add non chlorine shock each time I use the hot tub . Do I have to add “what ever it is” that established the bromine in step one above?

    • Hi Scott, you can establish the bromide bank of bromide ions, with Bromine Booster, which is sodium bromide. That is the quick way to boost it up, and then it can be reactivated by adding shock (chlorine or non-chlorine shock), to reconvert the bromide into bromine. However, many spa users also use bromine tablets to maintain the bromide ions and mainly use the booster after draining and refilling.

  9. What product do I use to shock a bromine hot tub. Most products I see have chlorine in them. Is it ok to use those?

    • Hi Terry, to reactivate bromide ions into bromine, you can use chlorine shock, or non-chlorine shock, either one will do the trick. If you are shocking to correct very poor water conditions (algae and bacteria), I would use the chlorine shock over the non-chlorine. Measure carefully in either case, it can be easy to overdose.

  10. Confused… the product to create a bromide reserve does not have sanitizer. What product causes test strip to have color. I added sodium bromine per instruc but it did not change or add color to test strip.i have floater w tabs too.i add non chlor after each use.

    • Hi Scott, we add Bromides, aka bromide ions to create the bromide reserve, as you say, yes. Shock or ‘non-chlor’ or MPS, nearly any granular oxidizer, can be used to activate the bromide ions, converting them into bromine, which is what the test strip measures. Before bromine can rise however, there needs to be enough of a ‘bromide bank’ built-up, or enough bromide ions in the water. Perhaps you need more bromides, or just need a good shocking, or maybe need more bromine tablets – or perhaps the test strips are to blame, old or contaminated.

  11. Ryan Diersing

    My total chlorine reads at max 10 and my free chlorine isn’t showing color at all meaning it’s at 0. I’ve been adding chlorine incrementally, but the free chlorine never shows any color on the strip. I read that I need to either non chlorine shock oxidize, or super chlorinate with 108oz of dichlor, but that’s like 13 cups of chlorine and that seems ridiculous. So how much MPS should I use to shock? Like 1.5 -2 oz for 450 gallon tub? And is that supposed to bring the total down and magically make free chlorine reading appear on my strip? It’s really confusing to add fresh chlorine andnit to never show up as free, or do I need a sufficient amount like 6tablespoons to get a base level, then just like a half teaspoon when needed with use?

    • Hi Ryan, wow – TC at 10ppm and FC at 0.0? The difference between TC and FC is mostly attributed to CC or combined chlorine, aka chloramines. At such high levels, you would also notice a very strong chlorine smell with the tub. Super-chlorinating or shocking is thr method to remove chloramines, by breaking apart the molecular combinations. You can use chlorine shock (cal hypo or dichlor), or you can use non-chlorine shock. They are nearly equal in oxidizing power, not quite 1:1, but close. You may want to consider draining and refilling, if a small shock makes no difference. Also be sure that the test strips are not faulty, test the water in another method, either with new kit, or take sample to a Leslies pool store or some place that does free water testing. If correct, look for the source of the problem, something in the water (ammonia, nitrogen, other chemicals) is causing free chlorine to quickly combine with others, becoming useless. If not found, switching to bromine may help.

  12. Hi Davy, I use the “Frog” system. I still have product left in the containers but starting to find blackish spots on the pillows and covers? Also, totally confused about Initial shock treatment and weekly shock oxidizing. I bought a weekly shock oxidizer but starting to think I am not supposed to use that with the Frog

    • Hi Michael, sounds like mildew, and it’s fairly common on pillows and covers actually. Some people remove the pillow every few months to give them a good scrubbing with 409 or soft scrub. The spa cover can be removed and sprayed with a light bleach solution, and rinsed off then left standing to dry before putting back on. With a FROG system (minerals + bromine), I would still shock the spa using a non-chlorine shock for spas, (or a chlorine shock for spas,) every time I used the spa, or every 7 days, whichever comes first. Just a small amount is needed, like 1/2 oz per 100 gals, (see label).

  13. Ben Merth

    How long should I wait to get back in after using a shock oxidizer? The label just says use when not in ise, but how long is that??

    • Hi Ben, if you are using a non-chlorine oxidizer, you can swim immediately. If you are using a chlorine oxidizer, either Cal Hypo or Di-Chlor, I would wait for at least one hour, and even then, wear goggles or keep heads above water. The concern is that undissolved granules can get into the eye or lodged behind the waistband of your swim trunks, which could cause some corrosion to soft body parts! Within a few hours, usually even the largest granules of pool shock should be dissolved. However it also depends on how much shock is added – it may not be wise to enter a pool with greater than 10 ppm of chlorine, it could bleach the suit or irritate the skin.

  14. Hey Davy,
    I have had my Bullfrog A7L for 3 years, and since I have owned it, I have had a very hard time trying to balance ta and ph. Upon fresh fill 2 weeks ago my ta was 30 and ph was 7.6. Once I added baking soda to raise ta, my ph was through the roof so I added ph decreases, got ph in line and all was good till this week when I tested my ta was at 40 and ph was at 8.0. I need your help, to figure out a real solution, other than over saturating my hot tub with chemicals and having to dump the water every couple months. It is a 450 gallon tub, calcium ppm is 250, ph 8.0 and ta is 40, bromine level is good 2.0 ppm. We do run the aerators on high, it is considered a therapy tub with jet packs. Your expert opinion and direction would be greatly appreciated.

    • Hi Craig, great question, thanks for asking. Next time you fill, I would approach the alkalinity in 3 to 4 separate additions, over 3-4 hours time, with the spa pump off, and cover left open, and add 1 ounce only of alkalinity increaser, leaving pump off. An hour later add another ounce, and so on. You could also do one dose per day as well, if that works better for you. For now, since the pH is at 8.0 now, lower the pH first, by adding just 0.5 oz of Dry Acid or pH decreaser (with the pump on low speed and aerators off), and then retest to be sure pH is around 7.2 before adding alkalinity increaser, and then add the bicarb in 3 to 4 additions.

  15. I bought a used 450 gallon spa and have been running it for 4 months now. I am just getting ready to change the water and I am wondering if I should super shock it before draining. The reason I ask is because it never seems to retain residual chlorine level in it. Here is how I ran the tub maintenance.
    1. Tub was filled brought to temperature and balanced for ph and alk, new mineral stick and bottle of enzyme was added to the tub.
    2. Regular testing and addition of chlorine or non-chlorine shock (brite) was added on althernating basis several times per week.
    3. Water would sometimes get foamy but it always seemed to be an issue of low alk and PH. Rebalance and all was fine.
    In summary, the chlorine level is always low if not pretty much at zero. Should I super shock the tub prior to draining at 10x the normal chlorine level (350 ml for a 450 gal tub)? Thanks in advance.

    • Hi Jerry, yes I would super shock it, even to 30 ppm (about 3 oz of chlorine shock)- very high to kill any biofilm or hidden bacteria that may be consuming the chlorine, or using it up. Used spas or any spa that has sat empty for longer than a few days, can grow biofilm in the pipes and jets. Most is discharged by running jets on high speed, but not all, it can grow in places that are sheltered from high velocity water. It develops a thick surface that resists normal chlorine levels. Run high chlorine for several hours, then let the spa sit open until the chlorine level drops, or add enough chlorine neutralizer to remove it, so you can drain the spa without affecting local ecology. you can also use products like Spa Purge and Jet Clean, designed to remove such biofilms from the pipes and equipment.

  16. I have a450 gallon salt water spa. I’ve drained and refilled it and I can’t remember if I can add shock at the same time as the salt or not? Also, I seem to have these yellowish floating things that feel like some sort of film that explode out of my jets once I start the pumps up after draining. I did drain and used a spa purge but then left it empty for over a month. Then just filled it and o see the same floaters. I’m removing them w a pool net/filter thing. What else should I do? Thanks!

    • Hi Josie, the floaters are what I call Bio-Film, a bacteria slime that forms on the insides of pipes and jets when left empty for weeks or months. I would drain again, and then use a small Drain King (from hardware store), attached to a garden hose. Dissassemble pump unions, or jets, to deliver high pressure water, in both directions, at as many points as possible, to dislodge as much as possible. Then Fill and use Spa Purge or Jet Clean, and then drain again (no salt needed either time of course). On the third fill, wait to add salt, and then shock the spa with a very high dose of chlorine to reach 30-50 ppm. About 40 oz of 6% bleach or 5 oz of chlorine shock Dichlor 56%, to super shock the spa. As chlorine level returns to normal, add salt and begin chlorinating. I would also replace the spa filter too – to be sure the spa is healthy and not harboring bacteria. Thanks, good question!

  17. Hi Davy, I filled my 700L Mspa with fresh water. I added 3oz of Stain Prevent let it sit for 1hour and then 3tbsp of shock. I also have a floater with bromine tablets is that ok??? Also it seems like every time i do this the levels stay ok besides for the bromine and free chlorine being hight for a few days then they almost disappear of the charts what should i do??

    • hi Jordan, one step is missing, adding an ounce of bromide ions after refilling the spa. It takes weeks for bromine tablets to dissolve enough bromide ions, which convert to bromine after shocking the spa. Add either Leisure Time Sodium Bromide, or our own Bromine Booster after filling and stain prevent, but before shocking, and you’ll see the bromine levels stay stronger for longer.

  18. Hi I over dosed my 250 gal hot tub with liquid bleach to shock. I have 2 ppm free chlorine but more like 10 total…..Is it safe to go in. I filled it with my well water and decided to shock a bit of iron came out of solution but I used like a cup of chlorine and now 2 days later I am off the charts!!! What can I do. If we use it that will cause a demand right? Is total chlorine dangerous??

    • Hi, when free chlorine is subtracted from total chlorine, the difference is called Combined Chlorine, aka Chloramines. If you have 8 ppm of CC, I would recommend you drain and refill the spa.

  19. Scott Cowan

    Hi Dave,

    Simple question…if using bromine tablets as a sanitizer, can you use liquid chlorine shock? Not sure about the chemical interaction here.

    • Davy Merino

      Hi Scott, when using bromine tablets, shocking the spa (with chlorine or non-chlorine shock), will activate the bromide ions, converting them into bromine, so you use fewer tabs. Many people use a chlorine shock like Spa56, or a non-chlorine MPS shock, but you could also use liquid chlorine to accomplish the same thing. If using 6% concentration, add 1-2 oz. per 100 gallons. It may raise the pH slightly after adding.

  20. rick robb

    my lazy z spa holds 800 ltres i use bromine tablets the reading is 11 how should i lower it i changed the water now its back to 11 i leave the floater with tabs in 24-7

    • Davy Merino

      Hi Rick, open the cover and let it breath, remove any floating cover too (very high bromine is bad for covers, as you may know). Secondly remove the floater of course, for now. You may need to use fewer tablets, just 2 or so at a time, perhaps, or adjust the baffle to release less bromine. The bromine will come down naturally over 24-48 hours with the cover open. You can accelerate it by draining a portion and refilling, just 50 gallons or so. There is a product that removes chlorine and bromine that we sell, called sodium thiosulfate, but you shouldn’t need it, just let it come down naturally. Using the jets on high, and the air blower will also help accelerate the bromine reduction

  21. Jean Duncan

    We have decided to switch spa products to Brilliance; specifically a bromine start up for bromine boost along with a Brilliance bromine granular product (instead of floating tabs). We were told that using the granular product will allow us to also use it as the oxidizer after each use. We are on county water so have also purchased the Brilliance Metal/Scale to put in at start up (and it recommends weekly as well) In your opinion, is the metal/scale necessary weekly? And, will the granular product be effective weekly to keep bromine levels balanced in addition to using it after each use as an oxider/shock? We have a 300 gallon spa which is used by 2 approximately 2-3x per week.

    • Davy Merino

      Hi Jean, thanks for the question. Not specifically aware of Brilliance, but your description was very clear… The metal/scale product is known as a sequestering agent, it locks up minerals and metals in solution, to keep them from coming out of solution and making the water cloudy, or depositing stains or scale. For some people on city/county water, the water comes out of the tap with low minerals and metals, or it is fairly soft (under 200 ppm calcium hardness), and with low levels of iron, copper, manganese, cobalt, the usual suspects for pool/spa staining. So it is a valid question, if you have low levels of minerals and metals in your water, then you really don’t need to use the stuff. But, if you do have elevated levels of calcium or salt (as in saltwater pools), or draw your water from a well, or have city/county water that does have high levels of either minerals or metals… then you may want to use such a product to control minerals, metals, cloudy water and hard water scale. And, you also want to add Stain & Scale chemicals weekly or every other week, per label, because it doesn’t last long, it breaks or degrades in 1-2 weeks usually.

      As for the granular product – the general notion is that tablets dissolve slowly, and as long as you refill when needed, it will create a consistent and constant level of bromine at all times. When using granular, 2 or 3 times per week, the bromine level shoots very high, and then gradually drops low, sometimes too low, and this method (in general) can produce peaks and valleys of sanitation which can allow some bacteria to grow. However, if Brilliance has some sort of time-release molecules or something that works to keep a constant level, then that’s good. I suppose your experience with the system will be the best judge. I would probably test the levels regularly, maybe twice per day for a week or two, to see how constant and consistent it is…

      • Jessica Scull

        Hi. We’ve had our first hot tub for 6 weeks. It’s a 6 person 445 gallon hot spring with Corona discharge ozone care system. There are 4 of us who use it every other day. The directions are 3/4 tsp chlorine granules and 1.5 TBS oxidizer alternating before every use. Then weekly 2.25 tsp chlorine granules. The ph, alk and hardness are always perfect. But the sanitizer levels are always down before I treat it. We’re have also had some foam. When we went back they told us that is normal for the fcl and the tho be down with that kind of usage. But after reading online I have my concerns. After the first month I cleaned the filters and the foam went away. 2 weeks late it’s back. Should I be cleaning the filters more often? Should I put the alternative chemicals in it daily whether we’re are using it or not?

        • Hi Jessica, to avoid peaks and valleys of chlorination, you could replace most of the chlorine granules with 1″ chlorine tablets, used in a floating spa-chlorinator. This will allow you to keep a consistent and constant level of chlorine in the water. Foaming can be caused from a variety of issues, and foam-down products don’t correct such situations, it just temporarily removes the foam. Are you also draining and refilling every 3-4 months? Or in your case with what could be called ‘heavy use’, maybe every 2-3 months would be more appropriate. Draining and cleaning almost always solves foaming problems in hot tubs.

  22. Alyson Ingle

    I received a Intel Inflatable Spa for Christmas and we just set it up last week due to the weather change. Its about 200+ gallons. We are using bromine tabs and we used a bromine starter. We are using the spa once a day, 2 people. Last night I noticed a large amount of foam in the spa. Reading on different sites it said to shock it first and then use a vinegar/ water/ baking soda mixture to remove the foam. This morning, I went onto a spa chlorine calcult or to figure out how much liquid shock to use and it said 200 gallons @ 2 ppm free chlorine use .3 gallons of liquid chlorine. I thought this was too much shock so I used about 2.5 cups of liquid chlorine. Now I am worried that my skin is going to melt off. Any suggestions?

    • Davy Merino

      Hi, foaming in spas is caused by lots of things, but is usually a mixture of dirt, oils, scale etc, combined with water chemistry that may be a bit off. Foaming water can be an indicator that a water change is not far off, and that is the best solution to foamy water. It can also be an indicator that (hate to say it), but you may be bringing in a lot of body oils, cosmetics, hair products etc, into the water. Showering beforehand is recommended, especially with such small filter systems. As for liquid chlorine, 2 oz of store bleach (6% strength) will raise 100 gallons to 10.0 ppm, a good shock level for most situations (use 30 ppm for algae and bacteria, which would be 6 oz per 100 gallons to reach 30 ppm). 0.3 gallons, as you mention, is too much, that would be 38 oz (!), which may melt your skin off, yeah. So you used 2.5 cups, or 20 oz. – so your water is about 50 ppm now (that’s high!). Leave the cover off, turn off the heat and let the pump circulate, but don’t get in until the chlorine is testable and below 5 ppm. Might take a week…? You could pump out half the water and refill, to increase turnaround time, but first let the chlorine naturally come down over a day or two.

  23. I’ve got a 400 gallon spa and I’ve been using bromine tabs & non-chlorine shock weekly for several years without issue. Usually 1 user several times a week, water replaced every 3-6 months, and regular filter cleaning.

    It’s been hassle free and I really thought I had maintenance nailed until several weeks ago where the water got cloudy and then really started to smell “funky”. I immediately drained and cleaned everything and filled it back up the next day. Gave it a bromine starter powder pack and a bromine tab floater, and then went on a business trip for week.

    Nobody used the spa while I was gone, but when I opened the lid to check on it, the most foul and disgusting smell hit me and the water is cloudy again. I’ve immediately drained it and heading out to clean the tub, but what the heck might be going on? Could it be some kind of bacteria/pathogen in the system that I need to treat in a different way right out of the gate? I was thinking about going to get some chlorine shock instead and doing that before adding any bromine since I hear it’s better on bacteria/pathogens… thoughts?

    • Davy Merino

      Hi, could be a change in your fill water perhaps, water quality can vary sometimes. If suspected, you could use a pre-filter. I suppose it could also be a bacteria build-up, or biofilm in the pipes. Using a product like Jet Clean or Spa Purge could help in those cases, as well as a heavy dose of chlorine shock (not much used, about 2.0-2.5 oz for 400 gallons). Chlorine shock will also reactivate bromides, just like non-chlorine shock. Good Luck!

  24. My 207 gallon spa turns green every couple of weeks even though I take the water to Pinch a Penny and have it tested every Saturday. I just tested it on Saturday, all was fine. It needed an ounce of PH down and 1.2 ounces of bromine booster. I added them and everything was clear. It rained Sunday so I went to get in spa tonight (Monday) and it has a green tint again. We are averaging draining it every 2-3 weeks. I am the only one who gets in it for approx 15 minutes every or every other night and was told to put in Chlorine Free Oxidizer every time I use it (about a capful). I do. I am ready to put it on Craig’s list. This is more trouble than it is worth. Nobody can answer WHY it keeps turning green so quickly. Yes, it is covered and it is about 104 degrees.

    • Davy Merino

      Hi Donna, I would look towards the filtration. If the circulation and sanitation is correct, the other leg of the 3-legged stool is filtration. Perhaps the cartridge needs to be changed, or maybe it’s not situated correctly, or locked in place properly, allowing water to bypass the cartridge. Or perhaps the cartridge is damaged. Maybe the filter pump is not running, only the circulation pump, if you have both. Or, if you have high levels of metals, they can give the water a clean green tint, but that doesn’t come and go as you describe… I would lean towards incorrect filtration, as the probable cause. Good Luck!

      • Davy, thanks for your reply. One clarification however is that I’m refilling with fresh water, which usually has a good amount of chlorine in it. Usually about 3ppm I believe which is a normal level for a spa. What I’ve heard is that it’s usually best to “burn off” the chlorine before building a bromine reserve, but if I have a bacteria or biofilm issue in the plumbing, what do you think about filling it and shocking first before I establish the bromine reserve?

        • Davy Merino

          Hi – yes I agree – burn off the chlorine and more importantly the chloamines – which can be high in some city water supplies – high chloramine levels can interfere with proper sanitation and could be a cause of your recent troubles. You could use a prefilter to remove chloamines, or shock the spa – as you say, before adding bromides.

          • I used a chlorine shock on the hot tub last night in the quantities you mentioned and got an appropriate reading of free chlorine. This morning (16 hours later) the free chlorine level is 0, total chlorine level is about 2.5 ppm, and the water is slightly hazy. Is this what would be expected after draining, thoroughly cleaning, and refilling the hot tub just yesterday morning or does it indicate a contaminant that I’m dealing with? I was about to add the bromine starter pack to build up reserves but the fact that all the chlorine is in a “combined” state threw me for a bit of a loop. In summary: cleaned and filled spa, initial reading = 3ppm free and total chlorine, shocked spa and had normal reading, 16 hours later the water is hazy, free = 0 and total = 2.5ppm yielding 2.5ppm combined.

          • Davy Merino

            Hi, when that happens… when you shock a spa heavily with chlorine – and the next morning the chlorine level is zero – that means that contaminants were greater than the chlorine added. Repeat again, with more chlorine this time, until you can maintain a measurable chlorine reading 12-24 hrs later. Also check pH – important to be in the 7.2 – 7.6 range when shocking -as chlorine is much more effective (active) with a low pH level.

  25. Our water becomes very cloudy after heavy usage (20+ people) in one day. We shock but water still remains cloudy. We did a full drain and refill less than 2 weeks ago. Should we do something different than 2 tablespoons of shock? It doesn’t seem to clear the water.

    • Davy Merino

      Hi Michael, yes I would shock it with a triple dosage after entertaining so many people. Or give the spa hour breaks, and shock a few times during the day, and let the filter catch up. Also check the pH level daily, as many people can throw it out of whack. And, your spa needs extra filtering, so be sure it’s running all the time for extra filtering. Change out the filter cartridge more often and change the water more often too. A supplemental sanitizer should also be used, like ozone or minerals. Enzymes and clarifiers can help too. Even if you have an 8-person spa, some systems can become overwhelmed with just 4-people daily, or everyday usage. Spa usage of 20+ people per day requires serious sanitation, filtration and possibly changing the water weekly, if not daily – to keep it safe and healthy. Follow commercial spa guidelines and be safe! you don’t want your guests to develops rashes and other infections…

  26. Mikael Fredstrand

    I wonder if you would recommend to change 1/4 of the water in the hot tub monthly instead of completely change the water every 3-4 months? This is in a rental unit.

    • Davy Merino

      Hi there – not a bad idea actually, and I know some folks that do it that way. In fact, it may be better to drain and refill incrementally, rather than waiting until the water really needs a full replacement. However, be prepared for those times when a complete replacement of the water is needed, for times when heavily used, or contaminated or power outage, etc. For most rentals, changing the water monthly (completely) may be needed, depends on how much the spa is used (or abused I should say). Use your judgement.

  27. Jordan Hintze

    I am extremely confused with treating my spa water. This is the first time in a few years I have used my hot tub. Here’s where I’m at: hot tub was drained and cleaned, then filled and a spa purge product used. After using the spa purge product I drained that water. Again cleaned out the hot tub. Yesterday I filled with new water and first used “Spa Stain and Scale”. After allowing that to work I used “Spa Metal Free”. Today, I tested my water and my pH was a bit high, but my alkalinity was a bit low. I used “alkalinity up” and let that work. Upon retesting, the alkalinity and the pH were predictably both high, so I then used leslie’s “Dry Acid” to lower pH and Alkalinity. Once my alkalinity and pH are in normal range I am confused on where to go from there. Should I put chlorine in as the next step or do an oxidizing shock? No Chlorine has been added at all yet and is chlorine is showing up white or absent on my test strip. Please help me! I’m so lost!

    • Davy Merino

      Hi Jordan, you are on the right track! Stain & Scale and Metal Free are used to lock up minerals and metals in solution, for spas on well water, and especially for plaster inground spas which stain more easily. If you don’t have well water, and don’t have a plaster (cementitious) finish, and don’t have a metal problem, you can skip it next time. And, both products do the same thing, so you don’t need both I wouldn’t think. For pH and Alkalinity, as you know both are related and adjusting one affects the other, so sometimes you have to see-saw with pH and alkalinity chemicals until both come into range (80-120 ppm for Alk, 7.2-7.6 for pH). Now for the sanitizer, chlorine or bromine. I would shock the spa first, using either a non-chlorine shock or chlorine shock, either one. Shocking is used weekly or so, depending on the spa usage, to remove bacteria, break down organics and other undesirable compounds. But you also need a Daily sanitizer, either the 1″ chlorine tablets in a small floater, or the 1″ bromine tablets, also in a small floater. use enough tablets to get a consistent and constant reading of 2-3 ppm of chlorine, or 3-5 ppm of bromine*. If using bromine tablets, there is one additional step, after draining the spa, shake in an ounce of Bromide Booster, to build up the level of bromide ions in the water, otherwise it can take weeks to begin to register a bromine reading. *If you also have a Mineral Stick (by Nature2, Leisure Time or Spa Frog), or if your spa has an ozonator, you can cut back your tablets by half, to run at 1-2 ppm chlorine, or 2-3 ppm bromine. Hope that helps!

  28. If I use Bromine tablets in my Hot tub do I have to use Bromine shock, or does it matter?

    • Davy Merino

      Hi Glen, in a bromine treated pool (or hot tub), shock is used for the normal reasons (removing bacteria, oxidizing organics, removing bromamines), but the larger reason is that using a shock oxidizer (chlorine shock or non-chlorine shock), will re-activate bromide ions into bromine, in a never ending cycle. Active bromine reverts to bromide after it has done it’s job, and the shock changes it back to bromine again. Another part of using bromine in a spa, is that it takes several weeks of using bromine tablets, before the bromide ion ‘bank’ builds up, so many spa owners add an ounce of Bromide Booster to the water after draining/refilling, to re-build the bank instantly. So… when using bromine tablets, you also need to shock every week or two, and after draining, use a bit of bromide booster. Thanks, good question!

  29. Melodyn Williams

    Also how much shock should I use for 320 gals

    • Davy Merino

      Hi, I like to use poolcalculator.com for such precise measures. For 320 gallons, using Cal Hypo shock, you would use 2 oz. to shock to 30 ppm, for severe algae. If the water looks good, and not completely green, 1 oz or even 1/2 oz. would be good. Basically a tablespoon of 65% cal hypo shock. IF you are using other types of chlorine (with different % of available chlorine), or non-chlorine shock, the amount would be different.

  30. Melodyn Williams

    My Sundance Marin states to turn on jet when adding PH balancing and shock why is this different then the recommendations stated above.TY

    • Davy Merino

      Hi, I see that the Dr. suggests turning off the blower and jet pump during shocking, to avoid the shock gassing off too quickly. pH adjustment it doesn’t matter so much, but alkalinity adjustment will favor calm water, for a more rapid exchange of hydrocarbons. Sundance would advise to have the jet pump running, to more quickly mix the chemicals, but more importantly, to make sure that large quantities of chemicals aren’t sitting directly on spa surfaces, undissolved, which could dull or harm the finish.

  31. Can I use liquid chlorine to shock in my 500 gallon spa w bromine tablets floating? What is the ppm I should hold daily? What should I shock up to (ppm) and how often when using 3-4 times a week.

    • Davy Merino

      Hi, yes you can use liquid, as a shock oxidizer, and also to reactivate bromides into bromine. For a 500 gallon spa use 6 oz of 5% bleach, to raise CL levels to about 5 ppm. For daily sanitation, keep bromine levels around 3 ppm, and shock the spa every week with about 3/4 cup of bleach, and see how that goes? You can also use non-chlorine shock after heavy use of the spa.

  32. We have just cleaned and refilled the spa, I have used the spa shock granules as measured and am running the spa on low
    Why do the granules just sit on the bottom or will they disintegrate?

    • Hi Jay, generally speaking, most MPS (non-chlorine) spa shock will dissolve instantly. Chlorine shock will take longer to dissolve completely, and can be pre-dissolved into a clean bucket or pitcher of water, and then added (always add shock to water, not water to shock). Also, spa shock that has been exposed to moisture may take longer to dissolve, and may have lost some of it’s power. For granules that sit on the bottom, in most cases they won’t harm the surface, but to reduce the risk, use a brush or net to stir them around.

  33. Mo Solomon

    When should I shock my hot tub???? Before draining down or after I have refilled?
    Thanks

    • Hi Mo, not before draining, unless you have a spa that has turned green or become stagnant. And not after filling, unless you suspect that the fill water may be unsanitary – which could happen. Shocking the spa is done for these reasons 1). To kill invisible bacteria and other pathogens that escape normal daily sanitation, and 2). To kill visible algae, mold or bio-film on surfaces, and 3). To break down contaminants like soaps, lotions, hair products, and 4). To remove combined chlorine (chloramines) and combined bromine (Bromamines), and 5). To reactivate bromide ions into active free bromine.

      Generally, most spa owners shock the spa every week or two, usually after exiting the spa. Follow label instructions, always use spa shock (not pool shock), and leave the cover off the spa for 30-60 mins afterwards. A good pH level of 7.2-7.6 is helpful to allow the shock to be most powerful.

    • Mo Solomon

      Hi Ryan….generally my hot tub is not in use from Monday till Thursday, can I give it a shock on the Thursday morning and how long after shock can it be used?
      I have a 1500 Ltr tub, what measure of shock should I use?
      Will the shock raise the bromine level???
      Thanks for your help Ryan.

      • Hi, how much shock you should use in a spa, depends on the purpose of the shock, and what type of shock you are using, and of course how much water is in the spa. It also matters how much the spa is used 1-2x per week, or 3-4x per week – because the more it’s used, and the more people that use it, the more contaminants (from us!) that the shock needs to oxidize. For just 1-2 people, once or twice per week, the contaminants should not be out of control, so a normal dosage can be used, once per week. Assuming that you don’t notice any adverse water conditions (smell, color, cloudy, algae, foam), a normal dosage is also indicated. For spas with many people using it, or with noticeable water problems, or if power was shut off for a few days or for pump/filter repairs – then you can increase the dosage of spa shock, up to double or triple the amount shown on the label. For heavy use spas, once weekly shocking may not be enough, some spas need it almost daily. Good filtration and water balance is also important, and can affect the amount and frequency of spa shock needed.

        For your spa, since you don’t it that much, a weekly shock is fine (assuming that your filtering all week long, and maintaining a bromine level). Non-chlorine shock may state that you can use the spa immediately after treatment, but I’d wait 20 minutes, to let it do its thing without introducing more contaminants (you!).

        Adding shock to a bromine spa will increase the bromine level, yes. That is, if you have a good ‘bromine bank’, or build-up of bromide ions in the water. Aside from bacteria and bromamine removal, one of spa shock’s main roles in re-activation of bromide into bromine. When shocking a spa, some of the shock is destroying contaminants, and some is boosting the bromine level, and a heavy shock can raise your bromine level very high for awhile.

        For your 1500L (400 gal) hot tub, consult your dosage on the label, but it’s probably 3-4 tablespoons, or 1-2 ounces (28-57 gm) per treatment. Your own experience is a good tool to use, knowing the spa, and how it responds to certain dosages (given good water conditions and water balance), and will help guide your hand in treatment.

  34. How long should you wait after the shock treatment? If the water is very cloudy, Is it bad to do both a non-chorine shock, wait, and then do a chlorine shock? How long should I wait in between ?

    Thanks,
    Eric

    • Hi, you could use both, but i would probably wait about an hour between adding. Just be careful not to overdose, on either types of shock. Keep the cover open after shocking, and be sure not to mix oxidizers (or other pool chemicals)…

  35. debbie sutter

    Good afternoon how much shock do I use in 210 gallons of spa water. Water has sat all winter is clear and is now warmed up.

    • Hi, I like to use poolcalculator.com for such questions. You can type in gallons at the top, then set your current and target FC (Free Chlorine levels), then select your shock type from the drop down menu and… in your case, if you wanted to shock it good, to 10 ppm, you could use 0.5oz of DiChlor shock, or 0.4oz of Cal Hypo 65% available shock. If using non-chlorine shock, also about 1/2 oz.

      However, always consult the label on the bottle for specific treatment and dosage guidelines. Your pH levels should be proper for best shock effect. When shocking a spa, turn on the jet pump, and leave the covers off, to allow chlorine to gas off (and not harm your spa cover). Wait to use the spa until chlorine drops below 5 ppm. If using non-chlorine MPS shock, you can recover it or use it almost immediately.

  36. Chris Widener

    How much shock (chlorine based) should you use for a 400 gallon tub?

    • I have a great formula for you – for 400 gallons, add 0.1 oz for every 1.0 ppm of chlorine you want. As you can see it’s very little. If you just want a little 1 ppm boost, add a teaspoon, or 1/10 of an ounce. Add a tablespoon full for a 4ppm superchlorination or 2-3 tablespoons for poor water conditions or algae. It doesn’t take much, use very little! By the way, we don’t recommend using pool shock for spas. Spa shock is much finer, suited for hot water, labeled correctly…The larger problem is that opened 1 lb bags of pool shock can be dangerous, the can spill, become contaminated or become wet – from open/closing the bag repeatedly, like you would for a spa.

  37. Mary Anne Johnston

    Why not use bagged if it’s measured into another container pre-treatment?

    • Hi Mary Anne, the reason we don’t recommend bagged shock for spas is because storing opened bags of shock can be hazardous, from spills, moisture and humidity or contamination. It also tends to be slow dissolving, or not as fast as shock made specifically for spas. Also, granular chlorine should not be used in containers or with scoops that have contacted other chemicals. The smallest amount of residue is enough to cause a reaction, including explosions and fire.

Comments are closed.