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Pool calcium hardness calculator
Calcium hardness matters most in plaster and tile pools. Low hardness lets water pull calcium from surfaces, and high hardness can leave scale. Pool guides commonly aim for 200 to 400 ppm.
To raise hardness 10 ppm
| Pool size | 77% flake |
|---|---|
| 5,000 gal | 10 oz |
| 10,000 gal | 1.2 lb |
| 15,000 gal | 1.8 lb |
| 20,000 gal | 2.5 lb |
| 30,000 gal | 3.7 lb |
Vinyl and fiberglass pools have no plaster to protect, so many owners accept lower levels there. Your builder or liner maker may have a target of their own.
When hardness is too high
There is no practical chemical that removes calcium from a pool. Replacing part of the water with softer water is the normal fix, though that will not help if your fill water is already hard. Keep pH and alkalinity toward the low end of their ranges to reduce scaling.
Add chemicals to water, never water to chemicals, one at a time, with the pump running. Wear gloves and eye protection, and never mix products.