Calcium Hardness is an essential aspect of your swimming pool water balance and should be checked regularly. (At least three to four times a year, after heavy rains and especially after draining and filling up your pool.) A high calcium level can cause scale (staining the pool surface) and if it’s very high,it could affect the efficiency of other chemicals in your swimming pool.
In a marble plaster pool, keep your calcium hardness at 200 to 275 parts per million, and if it’s a fibreglass pool, 175 to 225 parts per million.
Decreasing calcium hardness usually means dumping the water and topping up with fresh water. Some claim that there are chemicals on the market that can remove calcium from water, but the jury is out as to whether it just hides calcium from tests or whether it actually removes it from the water. To increase the calcium, add calcium flakes to the water.