The amount of calcium and magnesium dissolved in water; measured by a test kit and expressed as parts per million (ppm) of equivalent calcium carbonate.

Also called Muriatic acid when diluted. A very strong acid used in pools or spas for pH control and for certain specific cleaning needs. A by-product of the addition of chlorine gas to water. Use extreme caution in handling. See also Muriatic acid.

The most powerful disinfecting form of chlorine in water.

A family of chemical compounds, including Calcium hypochlorite, Lithium hypochlorite. Sodium hypochlorite, etc., found in various forms for use as a chlorine carrier in pool and spa water.