The calcium portion of total hardness expressed as calcium carbonate. Typically 65-75% of total hardness. Low calcium hardness can cause damage to pool surface and components.
Most of the hardness of your water supply is dissolved Calcium salts due to the water having arisen in Chalk or Limestone areas. Magnesium salts also tend to be grouped with Calcium in this description. Some hardness is good for your pool otherwise Calcium from sources such as tile grout will be dissolved. Conversely, too much causes scaling problems.
The calcium content of the water. Calcium hardness is sometimes confused with the terms water hardness and total hardness. Too little calcium hardness and the water is corrosive. Too much calcium hardness and the water is scale forming. One of the basic water tests necessary to determine water balance. Minimum level 150 ppm. Ideal range 200-400 ppm.