Hard pool water is often caused by the presence of too much dissolved material -- such as calcium, magnesium and sodium -- in your pool water. Too little calcium hardness (dissolved materials) in your pool water results in corrosive water that erodes pool tiles and grouting. Rust can quickly appear and change the color of the water to an orange hue. Too much calcium hardness results in scale formation on pool surfaces and pipes and gives the water a cloudy appearance. Removing hard water from your pool begins with testing its calcium hardness level so that appropriate action can be taken.
Test your pool water for calcium hardness, alkalinity, copper, iron, pH and chlorine levels two to three times a week. Use a water testing kit, which you can purchase from your local pool supply store or online. The recommended levels are as follows: pH: 7.2 - 7.8, chlorine: 1.0 - 2.0 ppm (parts per million), total alkalinity: 80 - 120 ppm, cyanuric acid: 25 - 50 ppm, calcium hardness: 180 - 220 ppm, and total dissolved solids: 500 - 5,000 ppm.
Test for calcium hardness, the source of hard water in a pool, by using a tester such as the LaMotte ColorQ Digital Water Tester or another branded tester that measures calcium hardness. Navigate through the tester’s menu to the “CH” or “Chlorine Hardness” function and fill a clean tube with 5ml of pool water. Add the appropriate number of chemical drops to the water to the tube (the LaMotte tester calls for 5 drops of CH1 and CH2). Cap the tube and shake it. Insert the tube into the tester to receive your reading.
Drain some or all of the pool water and refill the pool if the test reveals too high of a calcium hardness level in your pool water. Retest the water, as simple draining and refilling is the best way to correct calcium hardness and remove hard water from a pool. If it does not, add a sequestering or chelating agent to your water, which is available at your local pool supply store.