Swimming Pool Water Balance Problems

pool-water-balanceAs a pool owner, you know how much change occurs in your pool constantly, due to various chemicals, oils and swimmers.

Because your pool water is in a state of constant change, it is essential to check and balance the pool water levels.

Regardless of type of pool – commercial or residential, and no matter what size pool you have โ€“ a large community pool or a small above ground pool, all procedures are the same.

Simply put, Water Balance is the relationship of the different measurements of chemicals combined in the water. Precipitation, pollen, pollution, bather wastes and windblown dirt and dust are some of the inputs that cause the water to be in an ever-changing state. These inputs alter the water chemistry of your pH, total alkalinity and calcium hardness.

pH-3The pH level is the measure of how acidic or basic the water is. It’s a scale of 0-14, 7.0 is considered neutral. To put it in perspective, acid rain has a pH of about 4.4. The human eye is about 7.3, within the range of 7.2 – 7.6 that we use for pools.

alkalinityTotal alkalinity measures the hydroxides, carbonates and bicarbonates.Total alkalinity is recommended to be kept in the 80-120 parts per million (ppm) range for concrete or gunite pools, and 125-150 ppm for vinyl, fiberglass or painted pools. Alkalinity should be tested on a weekly basis.

hardnessDonโ€™t worry if your hardness is under 500 ppm. Anything significantly higher than this can cause scaling and cloudy water, or calcium crystals that deposit as small clumps. Low levels (<150 ppm) are also bad, and can corrode pool surfaces; pulling out calcium. 200-400 ppm is an ideal range for your Calcium Hardness level.


Now you may be asking, what are some symptoms of common pool water balance problems? How can I know what is possibly wrong with my pool? What can I look for?

pH: If your pH level is too low, this means your water is too acidic, and you risk damage to the pool surface and corroded metals. Acidic pool water also leads to pool stains. Acidic water irritates eyes and skin, and allows for a faster evaporation of chlorine.

When your pH level is too high, this makes your chlorine weak, and provides an ideal environment for algae to grow. It also makes it easier for calcium and carbonates to precipitate out of solution and make the water cloudy, or leads to scaling and crystalline deposits on the pool or in the pipes.

For pH, the ideal range to keep is between 7.2 and 7.6. In The Swim has both pH reducer and pH Increaser for adjusting pool pH levels. Keep both on hand, even though you may need to use one more than the other.

Alkalinity: When alkalinity is too low, you may begin to see corrosion and staining. Since it’s closely related to pH, low Alkalinity will cause your pH level to be erratic and inconsistent. This is known as “pH bounce”.

High total alkalinity (TA) makes it hard to adjust your pH level, and make it stick. The pH becomes resistant to change when TA is too high. This can also lead to cloudy water, green water and swimmer skin/eye irritation. You can also see damage to filter cartridges or grids.

Alkalinity ideally should range from 80 to 120 ppm. Alkalinity Increaser is used to increase levels of alkalinity in the pool, but to lower total alkalinity, you add an acid, or pH decreaser. Lowering TA is done in stages, as you may need to increase your pH, to keep it from dropping below 7.0. It can take several adjustments, to bring high alkalinity levels down.

Hardness: The amount of calcium that is dissolved in the water. When calcium hardness levels are too low, you have soft water, and can see pitting and corrosion of plaster, grout and even vinyl. Soft water also foams more easily.

High levels of calcium hardness means that you have hard water, which can come out of solution, mix with dirt, and stain your pool surfaces, depositing as scale or crystals. Very high levels will even deposit in the heater or plumbing, like plaque lining arteries.

To avoid soft corrosive water and hard scaling water, test and adjust to the ideal range of 200 to 400 ppm. To raise calcium hardness, add calcium chloride, aka calcium increaser. For pools in hard water areas, that may see 700 ppm out of the tap, there is no easy way to lower calcium levels, but you can tie them up in solution by using a Stain & Scale control product.

Total Dissolved Solids: TDS is the total of everything that has ever dissolved in your pool. It can build up in the water when evaporation occurs. In most cases, TDS is not a concern for water balance, but for some pools with “old” water, and especially indoor pools (no rain), TDS can begin to “choke” the water after many years without adding regular fresh water.

Without enough dilution, some pools may notice the corrosion of metals such as pipework and filters, and problems with sanitation and cloudy pool water. Control TDS by adding fresh water seasonally.

To reduce TDS in pool water where draining the pool is not an option, some areas of the country have mobile pool water recycling rigs, that will pump out the pool, filter it with reverse osmosis, and pump it back into your pool.

Cyanuric Acid: A chlorine stabilizer bonds with free chlorine in pool water. It protects from ultraviolet rays and reduces the loss of chlorine in the water. Cyanuric Acid (CYA) allows you to reduce the amount of chlorine that is needed to maintain minimum chlorine residual in outdoor swimming pools.

When CYA is low in an outdoor pool, it can be difficult to maintain a chlorine level on a sunny day with many swimmers, and chlorine levels can drop dangerously low. When CYA levels are too high, over 50 ppm, problems can occur in maintaining chlorine levels sufficient to kill bacteria and algae.

Keep your CYA levels in the range of 25-50 ppm, by adding liquid or granular stabilizer to the pool. If levels exceed 50 ppm, lower by diluting the pool, or replacing 20% of the water.


TESTING-THE-WATERS - image creator not knownTest Strips, Test Kits or Digital Testers? If you want high accuracy, choose a Taylor or LaMotte test kit. Test strips from AquaChek or Insta-Test offer speed and convenience.

Digital pool testers offer the best of both, highly accurate and quick testing, with an exact digital measurement displayed.


~ Being in charge of a pool comes with many benefits and responsibilities. You stand between your swimming pool and your swimmer’s health! Make sure swimmers leave the pool as healthy as they came. Test your levels frequently, at least 3x per week, and make chlorine and pH checks daily.

If you are experiencing pool water balance problems not covered here, feel free to reach out to anyone of our pool chemistry experts in our call center, or send an email to Dr. Pool, our resident chemist.

Alex Malamos
InTheSwim Staff Blogger



Swimming Pool Water Balance Problems — 30 Comments

  1. Hi Davy. Need help please
    Total hardness : very high (1000)
    Total chlorine : very high (10)
    Free chlorine : very high (10)
    pH : very low (6.2)
    Total alkalinity : very low (0)
    Stabilizer : low (0)

    Pool is running high the last 3-4 days after treating for about 12-16 hours a day. Pool is cloudy but blue. Could kind of see near the bottom though. Did use some pool clarifier and phos-free. Any help would be appreciated.

    • Hi there, ouch! OK… any possible way to drain and refill with better water? ๐Ÿ™‚ If possible even to replace 1/4 of the water, that would be a good start, but if not I understand, and I would start on Alkalinity, adding Alkalinity Increaser (bicarb) to the pool, at a rate of 19 oz, (1 lb 3 oz) per 10,0000 gallons, to raise 10 ppm. You will need a Lot! And also need a reliable test kit with Titration TA test, like the K2005 test kit. Add the Bicarb in 3 or 4 smaller doses, not all at once, to avoid sending the pH level thru the roof, which could cause more cloudiness and scaling. Brush the deep end for a few minutes, then turn on the pump again. Adding so much bicarb will raise your pH, so after a few hours of circulation, re-test Alk and pH, lower pH if above 7.8, using pH Decreaser (acid) and then add more bicarb, until you get 80ppm TA and a pH of 7.2-7.6. It can take a few days sometimes, try to remain patient!

      By this time, the chlorine level should have dropped to within normal range. Add a bit of cyanuric acid, 2 lbs per 10000 gals, to establish a base of 20 ppm, important to protect chlorine from the sun during the day time. The hardness is very high at 1000, which can cause bouts of cloudy water, scaling stains on surfaces, and other water management problems. Dilution is the Solution, again if possible to add softer water, replacing some of the water. Also avoiding cal hypo pool shock, which contains calcium. But most importantly, using a good sequestering agent, every 2 weeks like clockwork, to keep scale minerals locked in solution, where they can’t come out to play.

  2. 14,000 24 ft above ground pool, pump constantly running and filter cleaned 3 times this week,vacuumed, added chlorine and tablet, went from very low to very high, still greenish. Added shock and 1 gallon of muratic acid. Reads high ph, High alkaline,High chlorine and everything else normal range. I am baffled.

    • Hi Sarah, when chlorine levels are very high, it can affect the pH test, making the pH appear to be very, very high. Since you added a gallon of acid (?), it should be very, very low actually. If you have a full test kit, like a Taylor with 3 bottles for testing alkalinity, the first bottle is a chlorine neutralizer- you can add a few drops to your water sample before testing pH, to remove the chlorine interference, as it’s called. In most cases, if the pool is still greenish, you may need more chlorine, if not changing to blue rather quickly. Good chance that your filter is struggling. Might need a new filter or filter sand, either now, or just after clean-up.

  3. Hi Davy,
    My pool 20,000 gallons water was too old, I DRAINED ALL WATER and REFILLED with fresh water.Please help me how to start to add chemicals to bring water balanced….


    • Hi Ha, Start with Alkalinity and pH levels, testing and adjusting to 7.4 for pH and 100 for alkalinity, then test calcium hardness and cyanuric acid, and adjust calcium to 180 ppm and cyanuric to 20-50 ppm. Start adding chlorine tablets immediately, and after balancing water you can shock the pool if it looks hazy or dull.

  4. Hey there. The pH in our pool has a high reading. Just wondering how to lower the pH level. Our pool is blue but cloudy. We cannot see the bottom. Any insight would be great. Thank you

    • Hi Abbey, pH is lowered by using an acid, such as pH decreaser (sodium bisulfate) or the liquid muriatic acid. A nice test kit like the Taylor K2005 can do an “Acid Demand” test, to tell you exactly how much chemical to add, or you can use poolcalculator.com to compute the amount needed, or consult the pH decreaser label. Just add directly to the water, and test the pH again after a few hours of running the pump. If your pH is erratic, moving all over the place, the Total Alkalinity may be too low. If your pH is difficult to change, you lower it but it pops right back up again, your Total Alkalinity may be too high – TA should be 80-120 ppm – so if you have to struggle with your pH level, check the alkalinity. A pH level of 7.2-7.6 is best, to help chlorine work most effectively, and to control scale and cloudy water. When pH rises, calcium likes to come out of solution, and cloud the water, or deposit itself as scale on surfaces…

  5. I can’t get the levels balanced in my pool what else can I do, it’s showing 0 chlorine 0 free chlorine 6.8 ph total was ok now is reading high stabilizer 0 we have tried everything and nothing is working

    • First thing is to add some granular chlorine, or liquid bleach for smaller pools, to raise the chlorine quickly. then get to work on the pH, adding enough pH increaser to raise the pH out of the acidic range, and slightly alkaline, in the range of 7.2-7.6. If you have trouble raising it and keeping it up, check the alkalinity, it may be too low or too high – should be 80-120 ppm. For the cyanuric, using trichlor tablets will add a little bit at a time, but on a freshly filled pool, adding flake cyanuric acid will raise it, 1 lb per 10000 gallons will raise it 10 ppm. Maintain cyanuric acid in the 20-50 ppm, so only 2 lbs is needed, per 10K gallons, to start. Then tablets will add more over the summer. Use enough tablets in a floater or feeder to maintain a constant and consistent 1-2 ppm of free chlorine in the water, verified by your testing. Add shock chlorine if you see algae, suspect bacteria, or have a discernable difference in total chlorine and free chlorine readings (which is combined chlorine or chloramines), or if you forget to add tablets and it drops to zero, or if the filter or pump system is not working. Speaking of – be sure to run your filter long enough each day, depending on it’s size and performance, it needs between 12-24 hours per day, to filter effectively, during summer.

    • Hi Adrian, it will come now naturally, over the next few days. There is a chemical Sodium Thiosulfate that will remove chlorine, if you need to do it instantly. Running the pump and removing any pool covers will help speed up the natural process.

  6. My pool has been green for a week. I used green to blue x 2 and vacuumed my pool today and the water is finally looking clear. When I check the ph is orange (I used a liquid tester kit) I know it is off the chart but I don’t know if it means too high or too low. When I checked the chlorine it also is clear which is not on the chart. What do I do now??

    • Hi, If the pH is yellow-ish, it’s low, if it is violet-ish it’s high. Nicer test kits have acid demand and base demand tests, done with the ph sample, to know how much to pH chemical to add. If the chlorine test is clear, that means no chlorine usually. Add a few chlorine tablets to a floater or chlorinator, to maintain a constant and consistent 1-2 ppm of chlorine in the pool, at all times. To give it a boost, since chlorine is near zero, add a lb. of pool shock, to boost it quickly, it will take too long for tablets to dissolve, then water will go hazy, and green again. Keep the chlorine high and the pH low, for best results in killing algae.

  7. The test I have only tests pH and Chlorine, both seemed to be off the chart, pH being too low, and chlorine being too high. It’s a large outdoor pool and it’s clean and clear. Yet the water is green! I have about 10 tablets in the pool.

    Any ideas what I should try?

    • Hi Joe, clear and green can mean metal contamination, not algae. Treatment for such would be to use a sequestering agent like Safe-N-Cleanor Stain Away to keep metals and minerals locked up in solution. Follow label instructions for application, and maintenance doses, as it will deplete over time, usually in 2-3 weeks. Another good product is Culator, which traps metals in a packet or pouch.

  8. After testing my pool liquid test solutions and confirming with with test strips, I have to add one quart of acid almost every other day.

    Do you have any suggestion to help correct this pH problem? The pool is not recently filled.

    Today’s test results are:
    Total Hardness +-1,750
    Total Alkalinity = 175
    CYA = +-150

    Any knowledge you may be able to share would be appreciated,


    • Bob, you need to drain the pool, those readings are off-the-chart high. The problem with your pH is caused by your high alkalinity, should be only 80-120 ppm. It’s buffering the pH too much, causing a strong resistance to change, so it’s not surprising that it’s hard to adjust. The total hardness coupled with the high pH problem can give you cloudy water, scaling and calcium deposits. the CYA at 150, makes your chlorine very sluggish and impotent, and the water is likely not as sanitary as you think, and it can lead to algae troubles. IF your readings are correct, I would strongly advise you to drain and refill at least half of the pool water. If that is not possible, use lots of acid to drop the Alkalinity back down, probably several gallons all at once, poured into the deep end, with the pump off for 20 mins, then turn pump back on. You can also try BioActive to reduce cyanuric acid down to 30 ppm, might need 3 treatments, at $50 a pop.

  9. Hi I just bought a new 10ft pool and I finally got in the alkalinity to the exact amount in the pH to the exact amount but my free chlorine is way up… how can I bring that level down?

    • Hi Trish, it will come down naturally, usually within 3 days. We do sell chlorine neutralizer (Sodium Thiosulfate), but that’s mostly used in commercial settings where the pool or spa must be operational for the guests or users. Remove any covers on the pool for faster reduction in chlorine levels, and to protect the cover.

    • Start by adding a bit of stabilizer (conditioner or cyanuric acid) to raise cya level up to at least 20 ppm, up to a maximum of 50 ppm. Next, drop your pH level to 7.2, which should lower the alkalinity as well. High alkalinity may resist the change, so you may need to lower pH several times, until both pH and alkalinity come into range (PH – 7.2-7.6 and Alkalinity of 80-120 ppm). Once those things have stabilized – then shock the pool, using 2 lbs of shock per 10000 gallons. Then you should be ok…?

    • Hi Deborah, there is a preferred order to water balance and shocking:
      1. Alkalinity First – 80 – 100 ppm
      2. adjust pH to the low end of the scale, 7.2-7.4
      2. Calcium Hardness – 180-220 ppm
      4. Cyanuric acid – 20 -50 ppm
      5. Shock – 10-20 ppm

      Chemicals should always be added on their own, separately. For a pool guy, charging by the hour, that’s often hard to do, but for a homeowner I would try to give the water an hour or two between each of the 5 steps above, or for each chemical added. This gives it a chance to adjust on its own without a lot of other chemical reactions going on at the same time.

      Specifically for shocking a pool, a low pH 7.2-ish is best for the ‘shock reaction’. Add in the evening or when the sun is not directly shining on the pool.

  10. Hi,

    I have a pool that is constantly green no matter how much chlorine or shock I add. I do have a slow leak in the pool. Pool is 5000-6000Gallon, in-ground cement wall. I add about 175 gallons of water every day which I believe about 1/2 is due to evaporation and rest is leak. Pump is run 8hrs a day. My PH level is constantly low (6.8) and chlorine level is always low even when I have 4-5 3″ chlorine tablets in the chlorine basket! No one uses the pool. Below are the measurements:

    tap water:
    Total alkalinity = 100

    Pool water= PH= 6.8 (raised it to 7.1 after adding 5lb soda ash!
    Alkalinity= 60 when PH is 7.1

    – Why is my alkalinity always low?
    – I assume my chlorine level is always low because Alkalinity is low which results in green?


    • I don’t think the low chlorine is related to pH or alkalinity. It does affect it’s potency, chlorine is much more active at a lower pH/alk, but does not affect the chlorine demand. Your pool either has a rather high chlorine demand, possibly from excessive debris, swimmers, animals or oils, possibly poor filtration. Could possibly be bad test kit reagents or bad test strips. And finally, it could be that the level of stabilizer in the water is so high (above 100 ppm), that ‘chlorine lock’ has occurred, making it hard to obtain a reading. It’s not the pH/alk, and it’s not the water loss – not really related to the no chlorine reading. Check your cyanuric acid level, if that is not the issue, and it’s not bad test strips, consider adding a Phosphate remover to the pool. If that doesn’t fix it, I would really shock the pool hard with granular chlorine, about 3-4 lbs, to see if it can break whatever is consuming the chlorine.

    • Hi Sylvia; Cyanuric Acid (aka conditioner or stabilizer) rises slowly over time, from the use of stabilized chlorine tablets, or all at once from an overdose of flake cyanuric acid. The correct level is 30-50 ppm, although it can be higher, but once approaching 100 ppm, chlorine becomes very lazy, and at such point, it needs to be lowered, to keep your water sanitary. There are two ways to do this, drain a portion of the pool, and refill with fresh water. Simple math – if your cya level is 100 ppm, and you replace half the water, you should end up at 50 ppm. A new chemical was introduced in the last year, called Bio-Active, which can reduce up to 50 ppm of cyanuric acid, at a cost of $50 per treatment.

    • Hi Ricardo, Check to be sure that your test kit reagents or test strips are fresh, and that chlorine is not sky high, both which can give false pH readings. As you probably know, acid lowers pH and alkalinity levels, so to lower alkalinity, you often have to raise the pH afterwards. If you didn’t drain, I would raise pH first, to 7.6, and then use acid to lower the alkalinity. 100 ppm is not very high, the range is 80-120 ppm, in most cases. The higher the alkalinity is, the more stable the pH is, or harder to adjust.

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