6 ways to lower pH level in pool

Ways to lower pH level of the pool

When the pH level of the swimming pool is too high, you have to lower it because there are risks and consequences which can be significant. We are going to see in detail 6 ways or products that can lower the pH level of the pool naturally or with chemicals, including muriatic acid and vinegar.

What is too high or too high a pH?

The ideal pH depends on each type of disinfection. However, there is a minimum below which is dangerous for the pool and swimming. Below this threshold, the water can sting the eyes and mucous membranes. A too low pH in the pool can also irritate the skin.

For example, the Victora state governement suggests a minimal pH level of 7 (source). The CDC is on the same line (source).

Standard:7 to 8
Recommendation:7.2 to 7.8

With a chlorine-treated pool, there is no additional problem with a low pH. The lower the ph, the more effective the chlorine will be (the ORP will raise), which allows disinfecting the pool even better.

With salt-water chlorination, the chlorine generator may require a certain pH level to work properly. The chlorine generator produces chlorine from salt, and chlorine, as we have seen, is much more effective when the pH level of the pool is very low. The minimum pH level for the chlorine generator can be found in the manual and it is often 7 or 7.2. It is quite rare to get a low pH level with a chlorine generator because this process tends to raise pH.

With a bromine-treated pool, it is the opposite of a chlorine-treated pool. Bromine loses its effectiveness with a lower pH. The pool will not be sufficiently disinfected and microorganisms or algae may develop.

Risks and consequences of a too high pH level in the pool

For humans, adults, or children, a pH that is too high in the pool can lead to irritation of the skin, eyes, and mucous membranes.

For pool equipment, it can also create problems because they have not necessarily been designed to work with very basic water.

For the quality of the water, it can be critical. With a pool treated with chlorine or salt, it will no longer be effective and the pool can then fill with small green algae, making the water cloudy and green. There is no such risk with a bromine pool.

Can we bath with a pH that is too high, too high, in the pool? If all the other water parameters are good and the pH is 7.4 or 7.7, yes it is possible to swim. On the other hand, if the pH is above 8.2 or if the other water parameters are not good, you should not go in the water!

How to measure the pH of the pool?

There are several ways to measure the pH of the pool:

  • colorimetric tests
  • electronic testers

Colorimetric tests are pH strips or tablets. It is very simple to use and very reliable. You dip the strip in water for 5 seconds, or you take a small quantity of water in which you put a tablet to dissolve. The problem is that you get a color indication that you have to transpose into a pH level. You can get a clear and precise pH level in the pool, but it indicates if it is more or less at an acceptable level.

Electronic testers are equipped with a probe to be immersed in the water. You get a precise and clear value of the pH level. On the other hand, the cheapest electronic testers may be unreliable. Moreover, the probe needs to be calibrated once a year and replaced every 3 to 5 years.

You have to test the water at least once a week, it is quite constraining. But it is important because the evolution of the pH over time is just as important as its level.

Why does the pH of the pool change?

The pH level of the pool is always changing. Every new element in the water changes the pH level. And it’s really everything: chemicals, insects, leaves, dust, rain, pollution, and also the swimmers.

Another parameter of the water helps to stabilize the pH level: the alkalinity (TA). The higher the TA, the more stable the pH will be, and the more chemicals will be needed to raise or decrease it.

What causes high pH in pool? Nothing is particularly the cause of high pH in pool. Salt-water chlorinator tends to raise the pH, slowly. Everything that goes into the water can be the cause of high pH: insects, swimmers, etc.

Products to lower the pH level of the pool

To lower the pH of the pool, acid products must be added. There are mainly 3 chemicals that help raise the pH:

  • muriatic acid
  • sodium bisulfate (or sodium hydrogen sulfate)
  • sulfuric acid

We always find one of its chemical products in the majority of “pH Minus” products for swimming pools. You can choose a pH minus product without dwelling on the chemical contained, it will be effective. If you want a treatment that is particularly suitable for your pond, it is useful to choose one of these chemicals specifically because they all have different effects.

Use. Always dilute acid in the water, never the other way around. For example, take a watering can half-fill with water and add the acid afterward. Never mix chemicals together!

Lowering pool pH with sulfuric acid

Sulfuric acid is found in most pH Less liquid products.

Particular care must be taken when handling sulfuric acid. Handling problems occur regularly, for example here in a municipal swimming pool. Always wear protective goggles and gloves.

Use. Liquid treatments are not recommended in manual treatment. It is rather intended for treatments carried out with a dosing pump. If you do it manually, pour the product directly into the basin, at the outlet of the return nozzles. Then, let the filtration run for at least 6 hours. Do not swim during this period.

Lowering Pool pH with Sodium Bisulfate

ph Minus products in the form of granules, or powder, are very often composed of sodium bisulfate.

It is a less dangerous form to handle than liquid sulfuric acid. This is why it is often the one chosen for manual processing.

Use. The sodium bisulfate powder (pH Minus) must be mixed in a bucket of water, mixed, and poured at the discharge nozzles. Let the filtration run for at least 6 hours and do not bathe during this period.

Lower pool pH level with muriatic acid (hydrochloric acid)

Muriatic acid, also called hydrochloric acid, is sometimes found in liquid “pH minus” products from certain brands. Muriatic acid is very effective to lower the pH level in the pool.

Muriatic acid is dangerous to handle. Gloves and goggles should be used.
You can also use hydrochloric acid to descale toilets. One can also this property if the pool has a little hard water.

Not too much at once. Avoid putting more than 50g/m³ of product in the basin. For example, for a 50m³ pool, you should avoid adding more than 2.5kg at once. It will be too big a shock for the water in the pond, and there is a big risk that the water will become cloudy. In addition, we always recommend going in small doses because the water balance of a swimming pool is very complex. Add only 50% of the required quantity and wait 24 hours to see the evolution of the water quality in the pool.

Bonus: lower the pH level with chlorine stabilizer

Warning, this way is only to be used in a very specific case:

  • chlorine or salt-water pool.
  • the water is new, or the water does not contain too much stabilizer

The pool stabilizer is necessary to maintain the quality of the water in a chlorine pool and, to a lesser extent, salt-water pool. The stabilizer is acid. And the acid lowers the pH level. It can therefore be used to lower the pH level in the pool.

More information about pool stabilizers here.

Lower pool pH level without chemicals

There is no method to lower the pH of the pool naturally, without chemicals. There are many sites that recommend using vinegar to lower pH level in pool. It really is a bad idea. Since vinegar is not a pure product, it will degrade the water quality in other aspects. But yeah, that’s true, vinegar will lower the pH level in the pool. But in the end, it will consume more chemicals to rebalance.

You can count slightly on rainwater which often brings a little acidity. But the effect is very measured.


Others informations about the pH level in the pool:


Pool pH at 8.2, what to do?

This is very high, even for a bromine pool! Do not bathe and add chemicals to lower the pH of the pool.

Sulfuric or muriatic acid for swimming pool?

Both products are very effective in lowering the pH and TA of the pool. As seen above, these 2 products are found in several commercial pH minus products. These are 2 dangerous products to handle, so you must wear gloves and protective glasses when handling them.

Does baking soda lower pH in pool?

Not at all. Baking soda is used to raise pH level in pool. More information here.

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