Hardness (Secondary Maximum Contaminant Level = 150 mg/l)
The presence or absence of conventional hardness in drinking water is not known to pose a health risk to users. Hardness is normally considered an aesthetic water quality factor. The presence of some dissolved mineral material in drinking water is typically what gives the water its characteristic and pleasant "taste". At higher concentrations however, hardness can produce white mineral deposits on tubs, showers, and dishes. Hard water can also reduce the efficiency of devices that heat water. As hardness deposits build in thickness, they act like insulation, reducing heat transfer. Hard water can also reduce the ability of soaps to create suds, thus reducing the efficiency of cleaning ability.
When adjusting a water softener, hardness is often expressed as grains per gallon (gpg). 1 gpg equals 17.1 mg/L.
For more information, please refer to the DES fact sheet:
WD-WSEB-3-6 Hardness in Drinking Water