calcs.homes
calcs.homes
Calcium chloride raises calcium hardness, protecting plaster and equipment from corrosive, low-calcium water. Enter your current and target reading for an exact dose.
Estimate only — pre-dissolve in a bucket of water before adding to avoid clouding.
We take the difference between target and current calcium hardness in ppm, divide pool volume by 10,000 gallons, and multiply by 0.125 lb — the dose of calcium chloride (77% flake) it takes to raise hardness 1 ppm per 10,000 gallons — which works out to about 1.25 lb per 10,000 gallons for every 10 ppm needed. We also convert the result to ounces, or grams in metric, since doses are often small.
This dosing rate matches the figure used across pool chemistry references and on calcium chloride packaging. Low calcium hardness makes water aggressive toward plaster and metal fittings, pulling calcium out of surfaces to compensate — the opposite failure mode of the scale buildup that comes from hardness that's too high — so keeping the reading in the 200-400 ppm range for plaster pools avoids both problems at once.
200-400 ppm for plaster pools; vinyl and fiberglass pools can run lower, around 150-250 ppm, since they aren't affected by calcium etching the same way.
Adding it directly and quickly can cause a temporary cloudy reaction. Pre-dissolve it in a bucket of water first, then pour the solution around the pool edge.