Kiz Posted January 11, 2009 Report Share Posted January 11, 2009 My test strips measure total hardness, which shows normal at 250. My test kit shows a calcium hardness that is low at 130. What is the difference? What does this mean? Quote Link to comment Share on other sites More sharing options...
chem geek Posted January 12, 2009 Report Share Posted January 12, 2009 My test strips measure total hardness, which shows normal at 250. My test kit shows a calcium hardness that is low at 130. What is the difference? What does this mean? Calcium Hardness (CH) measures the amount of calcium in the water. Total Hardness measures the amount of calcium AND magnesium in the water. Since scaling comes from calcium carbonate, it is CH that is relevant. Total Hardness isn't important or useful as a measurement unless you have no way of measuring CH directly and want an approximation where in some waters CH = Total Hardness / 1.4 which doesn't quite work with your numbers, but again it's just a rough rule-of-thumb. Measuring CH directly is the way to go. By knowing the CH, pH, TA, CYA, Temperature and rough TDS, you can enter these into The Pool Calculator to calculate the saturation index to see if your water has the potential to scale (positive index) or will dissolve plaster/grout and similar surfaces (negative index) or possibly be more corrosive though that is debatable. Richard Quote Link to comment Share on other sites More sharing options...
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