Regulating swimming pool pH is one of the most important aspects of swimming pool care. Low pH can lead to skin irritation and corrosion of pool equipment. High pH can result in cloudy water and contribute to scale formation. More importantly, high pH will reduce the effectiveness of the sanitiser as it releases less free active chlorine.

A1. What is pH?
It is a measure of how acid or how alkaline the water is. For example, lemons and cooking apples are sour and acidic and have a low pH. Soda crystals and bicarbonate of soda are alkaline and have a high pH.

A2. What are the yardsticks?
Swimming pool pH is measured on a scale of 0 (very acidic) to 14 (extremely alkaline). A reading of 7.0 is neutral.

A3. What should the pH of the pool water be?
Between 7.2 and 7.6, but keep it as near as possible to 7.2 if you are using Granular shock. This is a compromise as the chlorine would be more effective if the pH was slightly below 7.0, but this would lead to potentially corrosive conditions. Also, the human body is most comfortable bathing in water of pH approx. 7.4.

A4. Is accuracy important when measuring pH?
Yes – you should bear in mind the pH scale is not uniform. pH 8.0 is 10 times more alkaline than pH 7.0. pH 9.0 is 100 times more alkaline than pH 7.0. So small differences can be significant.

A5. What effects the pH of the pool water?
In some water areas, especially in the south of England, the water is hard because it contains dissolved calcium or magnesium salts and, therefore, has a naturally high pH. High water temperatures tend to raise the pool water pH; rainwater can lower pH. The type of sanitiser you use also has a bearing on pH.

A6. How often should I check the pH?
Preferably daily – but at least once a week.

TIP: In hard water areas it should be easier to keep pH within recommended limits by using our special Multi-fuctional pool tablets for hard water areas or our standard chlorine tablets rather than Granules. The tablets are slightly acidic in normal bathing concentrations and therefore tend to balance the hardness in the water.

TIP: When correcting out of balance water, always adjust the alkalinity first. This will make pH correction easier.

TEST METHOD: Dissolve a phenol red tablet in the pool water sample and take the reading by matching the colour of the sample with the colour on the comparator.

All of these chemicals including our leading own brand, Fi-Clor and many more. All are available in our large store in Esher, Surrey. Please contact us for further information. Order your test kit online or find out which test kit you need.