Water Hardness is created by dissolved calcium and magnesium, and is commonly expressed in mg/l CaCO3, or degrees of hardness.

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• 1 French degree of hardness ( TH ) = 10,3 mg/l CaCO3

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Hardness is never a problem for human consumption, but high hardness may lead to encrustation of pipes, and low hardness ( soft ) water may be corrosive.

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• AEP standard lower limit : 15 TH ( 155 mg/l CaCO3 )

• WHO recommendation : 100 to 300 mg/l

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