Calcium Hardness
Balance your pool's calcium levels to prevent etching (low CH) or scaling (high CH).
Target Range
Managing Calcium Hardness
Calcium Hardness (CH) measures how much dissolved calcium is in your water. Water naturally seeks balance; if it doesn't have enough calcium, it will eat it from your pool walls. If it has too much, it will spit it out as scale. The goal is to keep it happily in the middle (200-400 ppm).
Low Calcium (Aggressive Water)
Low calcium creates "aggressive" water. It will leach calcium directly out of plaster, pebble tec, and grout, leaving the surface rough, pitted, and permanently damaged. In vinyl pools, it can cause liners to lose elasticity and wrinkle.
Calcium Hardness Increaser
Increase water hardness.
High Calcium (Scaling Water)
When levels exceed 600-800 ppm, water becomes "scale forming." You'll see white, crusty deposits at the waterline, inside spillways, and most dangerously, inside your pool heater. Scale reduces heater efficiency and can eventually block flow entirely.
Maintenance Tip
Calcium levels are very stable and typically only rise due to evaporation (leaving calcium behind) or adding calcium-rich shock (Cal-Hypo). Test monthly, as you shouldn't need to adjust this often unless you have a leak or significant rain.
Pool Water Test Kit
Professional test kit.
Plaster vs. Vinyl Pools
The priority for calcium differs by pool type. For Plaster/Concrete pools, proper chemical balance is non-negotiable to prevent structural damage. For Vinyl/Fiberglass pools, calcium is less critical for the shell but still important for protecting metal equipment and preventing foaming.
How to Lower Calcium
Unlike chlorine or pH, there is no chemical you can add to simply "remove" calcium. The only effective solution is dilution: partially draining the pool and refilling it with fresh, low-calcium water.
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