If your pool water is hard, you risk the possibility of calcium building up and damaging your filter and pool pump. Fortunately, there are a couple of solutions for hard water problems and both should be available wherever you typically buy your pool maintenance supplies. These chemicals, like most chemicals used to treat pools, can be quite dangerous, so be sure to protect your skin and eyes with goggles and gloves before handling either of them.
Test the water's hardness using a pool testing kit. Normal levels range between 200 and 400 ppm.
Measure out an appropriate amount of trisodium phosphate or dry acid formulated for pool and pour into a plastic bucket. These chemicals come with specific instructions on the packaging for the amount of powder you'll need to use based on the volume of your pool. Pour water into the bucket and mix until the granules are fully dissolved.
Pour the chemical mixture into the pool and allow the water to cycle for a few hours before testing the water hardness again. If the hardness levels are still a bit high, wait until the following day before repeating the process.