The ideal level for pool water pH is 7.4 to 7.6. Water that is neutral – that is neither basic nor acidic – has a pH value of 7.0. This is mid-point on the 1 to 14 pH scale.
Above 7.0 pH, pool water is alkaline. The higher up the pH scale the pool water tests, the more alkaline it is.
Below 7.0 pH, pool water is acidic. The lower down the pH scale the pool water tests, the more acidic it is. Maintaining your pool slightly on the alkaline side (Note that the recommended 7.4 to 7.6 pH level is above the neutral point, thus alkaline) is important for a number of reasons.
When pool water is too alkaline (above 7.6) disinfecting chemicals work more slowly. They may not do their proper killing job even though tests of the water may indicate 9 proper residual. Also, scale may form on or in pool equipment and piping, and especially pool heater coils.
On the other hand, if pool water becomes acidic, it irritates the eyes, corrodes the equipment and piping, and can result in pool interior surface stains.
To test for the pH of the pool water, follow the instructions provided in your test kit. Do not add test chemicals directly into the pool and do not put the pool water back into the pool after testing. High chlorine residual in your pool can affect the water’s pH reading. If your test kit does not have a chlorine inhibitor, take the pH reading before adding chlorine. Do not hold your finger over the top of the test tube while mixing; body acid can cause a false test reading.