You know that pH is an important part of keeping your pool clean, but what, really, is it?

To understand pool pH, it helps to know that pH is an abbreviation for "power of hydrogen" where the p is short for the German word for power, potenz, and H is the element symbol for hydrogen. pH is the negative log of hydrogen ion concentration in a water-based solution, according to About.com Chemistry Expert Anne Marie Helmenstine.


When chemicals are mixed with water, the mixture can become either acidic or alkaline. pH asseses the relative acidity or alkalinity of water. On a scale of 1 to 14, where 1 is extremely acidic and 14 is extremely alkaline, 7.0 is neutral (pure water). Ideally, pool pH should be somewhere between 7.2 and 7.8. 

If water becomes very acidic - from adding too much acid, sweat, urine, or from too much acidic dirt and leaves -- it also becomes corrosive. Conversely, if water becomes too alkaline, calcium deposits (known as scale) can form in the pool's plumbing, equipment, and on pool surfaces.

pH also determines the effectiveness of the pool sanitizer and can be adjusted with various forms of acid, to bring down a high pH, or alkaline, to raise a pH that's too low.

To test pool water's pH, use a test kit or strips.