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. 

Though these pH lowering chemicals such as Hydrochloric Acid should be available at your local pool shop. Though if you're looking at raising your alkaline, we do have chemicals such as Alkalinity Up that are able to do this. 

Zodiac pH Down Tablets 2KG - Pool Acid Chemical Reducer

Shop ph Down Tablets here

1. 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!

2. 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.

3. Less chlorine odour

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.

This is one area of enquiry we regularly receive, but it’s easily fixed and we’re just a phone call away and always available and happy to give free advice! Call (02) 4322 2918 for advice on a strong smelling pool!

4. Less algae

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! Check out our Clarifier, Phosphate Remover and Algaecide for a clear and algae free pool fast!

5. Water 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.

How much acid is needed to reduce your pH? Firstly, it’s necessary to buy a cheap and basic water test kit.

Do the simple pH test on the water. If you’re using liquid or powdered chlorine, your pH will be either okay or most likely above pH 7.6.

If you have a smallish backyard-type pool (up to about 80,000 L) and the pH is, say, 7.8, have the circulation pump going, then using gloves and a face shield, add 500 mL of acid (hydrochloric) directly to the pool along the side. Do this when there is no one about, especially children, and do yourself a favour and have a hose with running water close by to rinse off and dilute any spills.

After 5–7 hours of water filtering, do another pH test. If, for instance, the pH is now 7.4, you know that 500 mL of hydrochloric acid will lower the water in your pool by pH 0.4. Now you’re controlling your pool’s chemical addition correctly, which will lead to safe and comfortable swimming. It’s that easy!

With pH being so important for proper water quality management, ensure that you keep on top of it by test and correct chemical addition. If you have any problems after that, we’re available!

Please see a list of other useful pool blogs below


Note: This blog is a rough indication of advice for an average sized pool and average dosing recommendations. Mr Pool Man always recommends getting your water tested by a pool professional before adding any type of chemicals for your own safety, or giving us a call on 1300 511 901 or contacting us if you are unsure. Mr Pool Man does not take any responsibility for incorrect dosages

Post author:

Natalie Hintze

Head of eCommerce & Marketing at Mr Pool Man,
Co-Founder at Water TechniX


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