Calcium Hardness

Also Known As:

When too much calcium is present in the water, scaling — or water deposits — can appear on the pool walls and equipment. When there is too little calcium, surface pitting is possible. It is important to keep a pool or spa’s water calcium hardness at the proper levels.

When calcium hardness is too high, the water might look cloudy. However, if the alkalinity or pH compensate for the hardness, there may be no change in the water’s appearance. As the excess calcium leaches from the water, a crusty, gray or white scale will appear on surfaces. Also, calcium deposits may pick up the tint of decaying matter and appear brownish looking like a stain on the surface of the pool. These deposits can be abrasive and provide good homes for microorganisms. They can also clog filters and reduce water pressure. Scale on pipes or coils can slow heat transfer, making the pool more expensive to heat and possibly causing the heater to fail.

When calcium hardness is too low, water can leach calcium from pool surfaces, particularly concrete, which may then resemble elephant hide This results in concrete pitting, plaster etching and grout dissolution.

Clearly, maintaining calcium balance is critical to a pool’s health and swimmers’ safety. The deal range is 200 to 400 ppm, with a minimum of 150 ppm. Calcium hardness should be checked monthly. Poolside kits are available, as well as computer analysis via a pool services company or retailer. Test strips offer limited results, while drop tests offer the true calcium concentration in 10 ppm increments.