Hardness Information



What is Water Hardness?

Water Hardness is a measure of mineral content in water. Hard water is formed when water flows through deposits of limestone and chalk which are made up largely of calcium and magnesium. Hardness is determined by the concentration of multivalent cations, which are positively charged metal complexes with a charge greater than +1. Common cations in hard water are Calcium (Ca+2) and Magnesium (Mg+2). There are two types of hardness, temporary and permanent. Temporary hardness is caused by the presence of dissolved bicarbonate minerals. Temporary hardness can be removed by boiling the water or through the addition of lime (calcium hydroxide). Permanent hardness is caused by the presence of calcium sulfate/calcium chloride and/or magnesium sulfate/magnesium chloride. These compounds do not precipitate out as temperature increases. Permanent hardness can only be removed using a water softener or ion exchange column.

Hard water causes soap to precipitate soap scum instead of lather because the 2+ ions destroy the surfactant properties of the soap. Hard water also forms mineral deposits, called scale, that buildup in pipes, restricting flow which clogs the plumbing. Hard water in swimming pools gives a turbid or milky appearance.

Health Risks

The World Health Organization says that there is no convincing evidence that water hardness causes adverse health effects in humans. The US National Research Council even found that hard water serves as a dietary supplement for calcium and magnesium. While hard water is not harmful to human health, it can cause skin dryness and tightness as well as dry and brittle hair.

Measuring Water Hardness

The products we carry to measure Water Hardness can be found HERE.

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