Understanding pH

pH is the measure of how acidic or basic or alkaline something is.

The pH scale runs from 0 (extremely acidic) to 14 (extremely basic). A pH of 7 is neutral. You are familiar with acids and bases from your everyday experience. Vinegar and lemon juice are mild acids. Cleaning solutions with ammonia and laundry bleach are rather strong bases. Human tears are almost pH neutral. The ideal range for pool/spa water is between 7.2 and 7.8.

Water with low pH can result in etched plaster or wrinkles in a vinyl liner; staining on the floor and walls caused by dissolved metal fittings and equipment; and pitted concrete. Low pH also promotes chlorine loss.

Water with high pH can lead to scaling. Cloudy water can be an early sign. Soon crusty white deposits will start appearing on surfaces, begin to plug up circulation piping and the filter, and gradually coat heating elements thus reducing heat transfer and eventually causing failure of the heater. Also when water has high pH, chlorine is not very effective at germ killing.

Both extremes—high and low pH—cause eye and skin irritation, something which is often wrongly blamed on too much chlorine.