Hardness in Drinking Water

Negative Aspects

There are no known health risks associated with the consumption of hard water. In fact, studies have shown that people who regularly consume hard water throughout their lifetime have a lower rate of cardiovascular disease.

There are some problems associated with hard water. These include:

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Hardness is not a specific constituent of water. It is due primarily to the presence of ions of calcium and magnesium in water.

Hardness is expressed in terms of calcium carbonate (CaC03). Water with less than 75 milligrams per liter (mg/l) is considered soft, 76-150 mg/l moderately hard, and above 150 mg/l, hard water.


The most common method of removing hardness from drinking water is the installation of a water softener. A water softener replaces the calcium and magnesium molecules with sodium molecules. For every milligram of hardness that is removed, 0.46 milligrams of sodium will be added to the water.

Studies have shown that elevated levels of sodium in drinking water may have an adverse affect on health. Persons who suffer from high blood pressure or are on a sodium restricted diet should not drink water containing greater than 20 mg/l of sodium without first checking with a physician. A simple solution to the problem of consuming softened water is to have the kitchen cold water faucet bypass the water softener.

Softeners are commercially available in a variety of sizes and types. Softeners are offered in automatic, semi-automatic and manual modes. Fully automatic softeners regenerate (backwash, brine and rinse) and return to service on a pre-set schedule. Semi-automatic softeners need to have the regeneration started manually but the rest of the cycle is automatic. Manual softeners require the manual operation of one or more valves during regeneration.

The size of the softener is determined by the amount (grains) of ‘hardness’ and the daily volume of water used. A softener rated at 20,000 grains of ‘hardness’ will soften 1000 gallons of water with a ‘hardness’ of 20 grains (1 grain = 17.1 mg/l).

The waste water from the softener backwash process must be disposed of with care. Since the potential exists for contamination of nearby wells with sodium, the underground disposal should take place downhill and as far as possible from the well. If a sewer exists, it should be used to dispose of the backwash.

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