water hardness units

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water hardness units

Postby Karen » Mon Mar 03, 2008 6:49 pm

Hi I am trying to find a formula to convert KH and GH harness measurments from ppm to degrees of hardness??

Any takers??

Postby Guest » Mon Mar 03, 2008 8:17 pm

1 degree of hardness = 17.86 ppm CaCO3

1 degree of hardness is defined as 10 mg/L of CaO, whereas the US ppm system is based on CaCO3. 10 mg CaO and 17.86 mg CaCO3 contain the same amount of calcium.

A rather math intensive derivation is given at

(replace all the "*" with ".", I had to trick the censor that doesn't want me posting links.)

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