Calcium Hardness

Calcium Hardness (or Total Hardness), as the name implies, refers to the hardness of the water, measuring the amount of mainly calcium and also other minerals. Swimming pools require hard water – defined as water with more than 100 ppm of hardness ions.

Like pH and alkalinity, calcium hardness affects the tendency of pool water to be corrosive when it is low and scale forming when it is high. Generally, calcium hardness levels should be kept between 200 and 400 ppm. If the hardness reading is too low, you will need to add Calcium Chloride to the water, typically packaged as “Hardness Increaser”, “Hardness Up ”, or “Hardness Plus”.

If your hardness level is too high (generally over 500 ppm, depending on your region), you may need to drain your pool partially or completely, as there is no chemical to lower the hardness level. If you typically have high hardness levels due to the tap water in your area, you may need to add a Metal Sequestering Agent on a regular basis to rid the water of excess amounts of harsh minerals.

Total Alkalinity		Enjoying Your Pool