What is pH and what does pH stand for?

It can commonly be one of life's (or the average pool owners) un-answered question. What does pH actually do and mean? Here we dive into the basics of pH and what the heck it has to do with your pool!

What is pH? Simplified, pH — little ‘p’ and capital ‘H’ stands for the measure of the activity of an acid or alkali in a liquid, such as pool water. The pH test actually measures the amount of hydrogen ions in the liquid.

Regardless of what the other tests are reading, a healthy pH should always be between 7.35 and 7.45. The pH scale measures from 0 to 14, with 0 being most acidic and 14 being most alkaline.

The pool chemicals that are normally used for the correction of pH are strong acids such as hydrochloric acid, sulfuric acid and sodium bisulfate. These are the acids used in swimming pools to lower the pH.

pH lowering chemicals such as Hydrochloric Acid should be available at your local pool shop since they're not allowed to be sent through mail. Another option to lower your pH levels is to get some pH down tablets, which are perfectly safe to send through the postal service. If you're looking at raising your alkaline, we do have chemicals such as Alkalinity Up that are able to do this.

Importance of Pool pH Levels

pH Affects Swimmer Comfort

It’s now established that the pH of tear drops from the eyes of normal healthy people is about pH 7.4. Surely, then, if we have the swimming pool water at this pH, swimmers shouldn’t get sore eyes from high or low pH water.

Trials we have completed with our pH pool testing kit have concluded that the comfortable range for pH in pool water is 7.6 to 7.2. You can expect severe eye irritation once the pH reaches 8+ or goes below 2- Ouch!

SEE ALSO: How To Treat Pool Water For The First Time

pH Affects Chlorine Activity

Whilst the activity of bromine in pools is only slightly affected by various pH changes, chlorine is greatly affected. At pH 8, only 20% of the chlorine in the water is sanitising, whilst at 7.4, 60% is sanitising. Lowering the pH alone can increase the chlorine’s activity, as many pool operators have found.

pH affects that "chlorine odour" or "pool smell"

At the recommended pH levels above, and with the increased chlorine activity, there will be less so-called ‘chlorine odour’ from the pool, as the now-activated chlorine kills off contaminants quicker than at higher pH levels. This chlorine odour, although smelling exactly like chlorine, is not actually chlorine, but the result of the chlorine acting on contaminants in the pool water and producing chloramines, which have this characteristic chlorine smell!

If you have a pool, especially an indoor pool, and you have this chloramine odour, maintain your pH between 7.35 and 7.45 using our generic pH test kit and keep the chlorine at about 3 mg/L (free chlorine, that is) and you should end up with better water and air quality.

Total dissolved solids (TDS), bather loads, water balance and possibly other things will all affect the water and air quality too, and sometimes these have to be addressed to get an improvement with indoor pool environments. This pH and chlorine test level will apply equally to an outdoor pool too, but chloramines tend to hang around in indoor pools and can make conditions uncomfortable.

pH Affects Algae Growth

Most algae is extremely chlorine-sensitive, so having the pH in the right range will allow for maximum chlorine activity and will kill off any algae.

If the pH and chlorine tests are at the right levels, as mentioned in the previous paragraph, then if algae remains, quite often there’s a problem with pool ‘dead spots’. If algae is noticed in the pool, wait until the pool is empty of people, obtain the correct protective equipment and a small quantity of calcium hypochlorite (powdered chlorine), sprinkle it dry over the area where you noticed the algae, and whammo! You’ve freed your pool of algae!

The right pH levels makes your water easier to balance

It’s easier to maintain your water balance correctly when you start off with the 7.35–7.45 pH range. Water balance done correctly is vital for proper water quality management.


So there are five sound reasons for maintaining the correct pool pH. It’s normal for those who don’t test and adjust it regularly to end up having important water quality problems. For more information on pH and how to adjust it and other pool chemicals, head on down to our Ultimate Guide to Pool Chemicals.

BONUS: It's Getting Cooler, Time To Winterise Your Pool!

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Happy swimming :)

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