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 – 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.

hardnessDon’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 — 10 Comments

    • 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.

  1. 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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