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 will 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, the water can sting the eyes and mucous membranes below a minimum level. A too-high pH in the pool can also irritate the skin.

For example, the Victora state government suggests a maximum pH level of 8 (source). The CDC recommends not going over 7.8 (source).

With a chlorine-treated pool, the chlorine loses effectiveness with a higher pH (the RedOx decreases). It will therefore take more chlorine to disinfect the pool. When the pH is very high, chlorine often no longer disinfects sufficiently. Microorganisms or algae then begin to grow. The pool can then become green and cloudy due to algae. So there are significant consequences to letting the ph go too high in a chlorine pool.

With salt-water chlorination, it’s like a chlorine pool with too high a ph. The chlorinator will produce a lot of chlorine to maintain good disinfection. The electrolysis process releases sodium hydroxide. Sodium hydroxide is commonly used in liquid pH+ products. Thus a salt pool often has too high a pH. A pH- pump is usually installed with a chlorine generator to control this effect. Finally, each chlorine generator indicates on the instructions the pH range in which it can work. It is better to respect this scale and lower the pH when it is too high to protect the device.

With a bromine-treated pool, it is the opposite of a chlorine pool. The higher the pH, the more effective and disinfectant the bromine is. Therefore, it is better with a high pH. The upper limit will mainly be that of swimmers. A pH of 8.2 should not be exceeded in a bromine pool.

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

For humans, adults, or children, a too-high pH in the pool can irritate 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. A pool treated with chlorine or salt will no longer be effective, and the pool can then fill with tiny green algae, making the water cloudy and green. There is no such risk with a bromine pool.

Can we swim with a pH that is too high in the pool? If all the other water parameters are suitable and the pH is 7.4 or 7.7, swimming is possible. On the other hand, if the pH is above 8.2 or others 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 straightforward to use and very reliable. You dip the strip in water for 5 seconds or take a small quantity of water in which you put a tablet to dissolve. The problem is that you get a color that you must transpose into a pH level. You cannot get a clear and precise pH level in the pool, but it indicates whether it is acceptable.

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

You have to test the water at least once a week, which is quite constraining. But it is essential 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 constantly changing. Every new element in the water changes the pH level. And it’s everything: chemicals, insects, leaves, dust, rain, pollution, and the swimmers.

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

What causes high pH in a pool? There are many reasons for the high pH in a pool. Salt-water chlorinator tends to raise the pH slowly. Everything that goes into the water can cause high pH: insects, swimmers, etc.

Products to lower the pH level of the pool

Acid products must be added to lower the pH of the pool. There are mainly 3 chemicals that help lower the pH:

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

We always find one of these chemical products in most “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 particularly suitable treatment for your pond, choosing one of these chemicals is helpful 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!

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, in municipal swimming pools. 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, usually contain sodium bisulfate.

It is a less dangerous form to handle than liquid sulfuric acid. That’s 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 and poured at the discharge nozzles. Let the filtration run for at least 6 hours, and do not swim during this period.

Lower pool pH level with muriatic acid (hydrochloric acid)

Muriatic acid, or hydrochloric acid, is sometimes found in liquid “pH minus” products from particular brands. Muriatic acid is very effective in lowering 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 use this property if the pool has 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 significant 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 water quality in a chlorine pool and, to a lesser extent, a salt-water pool. The stabilizer is acid. And the acid lowers the pH level. It can therefore be used to reduce the pH level in the pool.

You can read more about pool stabilizers here (Coming Soon).

Lower pool pH level without chemicals

There is no method to lower the pool’s pH without chemicals naturally. Many websites recommend using vinegar to lower the pH level in the pool. It 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 slight acidity. But the effect is minimal.

Other informations about the pH level in the pool:

• Ways to raise the pH level