Calcium and magnesium salts are the major cause of hardness in water supplies. Although not detrimental to health, hard water retards the cleaning action of soaps and detergents. When hard water is heated it will deposit a hard scale on heating coils and cooking utensils with a consequent waste of fuel. A water softening system is the most common method of lowering the hardness in water. The following is a scale on which to compare your water hardness; [0-75] low/soft, [76-150] moderate, [151-250] hard, [over 250] very hard.