WATER HARDNESS (HARD WATER)

Compare with water softener .Hard water is water contaminated with compounds of calcium and magnesium. Dissolved iron, manganese, and strontium compounds can also contribute to the "total hardness" of the water, which is usually expressed as ppm CaCO 3 . Water with a hardness over 80 ppm CaCO 3 is often treated with water softeners , since hard water produces scale in hot water pipes and boilers and lowers the effectiveness of detergents.