Hardness In Drinking Water
Hardness is not a regulated contaminant or water quality, but rather a subjective characteristic of water as it relates to washing, laundering, and its use in industrial cooling. Hard waters are said to be those that require large amounts of soaps or detergents in order to form a lather and be effective as a cleaning agent. Hard waters also tend to be scale-forming when used as coolant in heat exchangers.
Chemically, hardness is caused by a group of several significant divalent cations naturally found in water; hardness varies considerably depending on the geology of a region. In general, surface waters are softer than groundwaters. The significant hardness-causing divalent cations include: calcium, magnesium, strontium, iron and manganese.