Water Softener

A water softener is a device or a substance that removes, or renders inactive and isolates, ions such as calcium, magnesium, iron or manganese in hard water. Water containing dissolved calcium and magnesium salts, or ferrous iron, in amounts greater than 120 mg/l is considered hard. Hard water forms scale, a deposit of carbonate salts, on the inner surfaces of boilers, cooking utensils, and pipes that carry hot water or steam. Iron oxidizes, reddening the water. Mineral salts precipitate the fatty acids from soap in the form of a scum or a gelatinous curd.

Because of the problems created by hard water, both for industry and for domestic water users, various types of water softeners have been developed. Water passed through a polystyrene ion exchange filter gives up calcium and magnesium ions for sodium ions from zeolites in the filter. The addition of lime to hard water precipitates mineral salts. Borax and sodium carbonate are also precipitating softeners. Trisodium phosphate, once a major ingredient of detergent washing powders, is an efficient water softener but is no longer used of the pollution problem it creates.