What Raises the PH in Pool Water

The pH scale measures acidity and alkalinity. A value of 7.0 is neutral. Lower numbers indicate acidity and higher ones mean alkalinity. Pool water should be kept slightly alkaline at a pH of about 7.5 for water purity and swimmer comfort.

  1. Water

    • Water direct from the tap may be alkaline and raise the pH of the pool. This can happen when you initially fill the pool or when water is added to make up for evaporation and splashing.

    Plaster

    • In new pools, the plaster tends to impart a slightly alkaline bias to the pool water until it ages.

    Chlorinating chemicals

    • Some chlorinating chemicals such as sodium and calcium hypochlorite are highly alkaline and raise the pH of the pool. Automatic chlorinators in salt water pools also generate byproducts that cause the pH to rise.

    Environmental

    • The wastes deposited in the pool from swimmers and the residue of some algae growth can increase the pH.

    Adjustment

    • Other factors tend to decrease the pH of the water. To counteract these acidic influences on the water, pool owners add chemicals to force the pH up. The most common ones are granulated or powdered sodium carbonate (soda ash) and sodium bicarbonate (baking soda).