Excessive calcium, manganese and magnesium in pool water can cause scale-like buildup on the water's surface and in the pipes, plumbing and filter. These scales are not only unattractive, but irritating to swimmers' skin and eyes. High mineral levels can also build up in pipes and other pool components, necessitating costly replacement.
Test your pool water. If your water is connected to a municipal supply, call city hall or the water superintendent to determine the hardness of your fill water. If on a private supply, collect a sample of your fill water in an approved container and send it to your city or state health department to have it tested. If your fill water tests over 3 grains per gallon (GPG), you will need to have it softened. If your fill water tests under 3 GPG, your pool chemicals, not the fill water itself, may be causing water hardness.
Drain some or all of your pool water if the pool chemicals are causing water hardness. Refill with fresh fill water, and use a minimum of pool chemicals.
Add zeolite powder to your sand filter to absorb calcium molecules and soften pool water.
Add hardness reducers or chelating agents to your pool. Both are available at pool stores. Follow the directions on the package to determine how much to add to your pool water. These products will bond with and trap minerals that lead to water hardness.