Water is labeled hard if the total hardness is more than 7.0 gpg (120 mg/L). Total hardness is the sum of dissolved calcium and magnesium minerals in the water sample.
Drawbacks of hard water include scale build up on shower heads, water pipes and other plumbing fixtures, spots on glasses and utensils, deposits that form sludges in water-using appliances.
Hard water in washing machines and dish washers form scud and reduces cleaning effectiveness. Soap curd left by hard water clings to fabrics and causes them to become brittle.