Water that contains high levels of dissolved calcium or magnesium is described as being hard. The hardness of water is related to the dissolved minerals it contains, primarily calcium, magnesium and carbonate and bicarbonate ions these have a buffering capacity and resist pH changes. Hardness also affects the wetting ability of water and can damage equipment with a build up of calcium. Water containing more then 200 parts of these mineral salts is considered to high far effective chemical use.(Mg/l = milligrams per litre)
Water Hardness: Terms and Conversion