Total hardness vs calcium hardness

[brg88tx]

I have a HTH 6 way test kit from walmart. It tests total hardness. I always assumed that this was the same as calcium hardness, but i may be wrong. I do not have a calcium hardness only test, so i was wondering how much different the two can be and if there is a rule of thumb (like calcium hardness accounts for 80% of total hardness)? thanks

 

[brg88tx]

sorry i just found the answer to my question in pool school. guess i should have researched more before posting.

"TH - Total Hardness

Total hardness is the sum of calcium hardness and magnesium hardness. Most test strips report TH instead of CH. The ratio of calcium to magnesium varies. As an approximation you can multiply TH by two thirds to get a rough estimate of CH."

 

[JamesW]

If you have a vinyl pool, then it's only important to make sure that the calcium hardness does not go too high, as that could cause scaling. If you have a concrete pool, then you want the calcium to be higher to protect the plaster from deterioration. If your total hardness is high, or if you have a concrete pool, then it would probably be best to get a calcium hardness test kit. If you get your water from a utility, then it should publish a water quality report showing the levels of calcium and magnesium.

Example:
http://montgomerycountymud8.com/operati ... %20CCR.PDF
(Note that total hardness is reported in ppm CaCO₃, while calcium and magnesium are reported in ppm calcium and ppm magnesium. In this example, magnesium contributes about 16 % of the total hardness and calcium contributes about 84 % of the total hardness.)

This is just from your fill water, and the levels will be different based on what chemicals have been added, such as calcium chloride, calcium hypochlorite etc.

You might want to consider upgrading your test kit to one of the recommended ones for better overall test information.

pool-school/pool_test_kit_comparison