Hardness, total

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Terms & Synonyms

Official WHO Definition

Hardness in water is caused by dissolved calcium and, to a lesser extent, magnesium. It is expressed as the equivalent quantity of calcium carbonate. Hardness above about 200 mg/litre can result in scale deposition, particularly on heating. No health-based guideline value is proposed for hardness (WHO 2004). Caused mainly by the presence of calcium and magnesium in the water. Scale formation and excessive soap consumption are the main concerns. When heated, hard waters have a tendency to form scale deposits which shorten the life of water heaters and other appliances (Health Canada).

Other Definitions


Interpretations and Explanations


WHO (2004) Guidelines for Drinking-water QualityHealth Canada

WHO Lexicon page (translations and examples)

See also

External Resources


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