CALCIUM HARDNESS refers to the amount of calcium and magnesium carbonate <plus other minerals> in the water. In pool water, we are mostly concerned with the calcium carbonate level or calcium hardness (CH). It should be tested for and adjusted to balance with the total alkalinity of the pool water. Although “soft” water (low CH) is considered better for regular household use, soft water is not desirable in swimming pools as it is corrosive and damaging to your pool. Low CH causes plaster etching, dingy/dull/flat looking water, and the water could be corrosive. High CH can lead to scaling, clogged filters, bleached appearance of liners, heater damage, and cloudy water.

Maintain CH at 225 to 300 ppm for plaster pools and 125 to 200 ppm for fiberglass, painted, and vinyl-lined pools.

To raise CH, add “CALCIUM HARDNESS” after dissolving the required amount in 2 to 3 gallons of pool water.

Lowering CH is not as easy. CH can be lowered by 11 ppm through the addition of one pound of anhydrous trisodium phosphate per 10,000 gallons of water.

However, this method of treatment is not used since phosphates are nutrients for plant life and could enhance algae growth, add to alkalinity and upset the water balance. This is especially true if the source water has high CH. As pool water evaporates, the minerals stay behind and become more and more concentrated, increasing CH. Most source water has high CH, “METAL KLEAR and METAL GON” will help prevent scaling by “locking up” the calcium and keeping it in solution.

If the CH is always high in your pool (above 450 ppm) consult DownTown Pools for assistance.