water hardness
Hardness
is caused mainly by the dissolved mineral salts of calcium (derived from calcium carbonate (limestone) or mineral deposits of calcium sulphate) and magnesium (from dolomite), together with generally much smaller contributions from iron, manganese and barium salts. Hardness is generally expressed in mg/L as equivalent calcium carbonate concentration. Hard water may feel unpleasant in the mouth but it is generally accepted as safe to drink. The World Health Organization (WHO) has stated that "There does not appear to be any convincing evidence that water hardness causes adverse health effects in humans."
Soap will not lather in hard water and scale is formed on pipes containing hard water, particularly when the water is hot such as in boilers and domestic kettles. “Hard” water may be made “soft” by chemical treatment with zeolites and ion exchange resins. “Soft” water may possibly contribute to corrosion.
The ranges defining Hardness / Softness of water are imprecise, but the table below gives the general picture:
Hardness of water in Australia
Analysis of water hardness in major Australian cities by the Australian Water Association shows a range from very soft (Melbourne) to very hard (Adelaide). Total Hardness levels reported in various government reports are listed below:
