A testing kit will allow you to monitor your pool's pH level. There are a variety of different kinds of testing kits available; however, most versions for homeowners are either test-strips or reagent kits. For the reagent kits, you take a sample of pool water and add liquids or tablets to it. The water will then change color, indicating its chemical balance. For test-strip kits, you submerge the strip in the pool for a few seconds; it will change color due to the dyes it contains. Next, to determine the pool’s pH level, match up the strip to a color chart. Then use this information to determine what kind and how much of the chemicals your pool needs.
If you drain your pool once the swimming season has passed or to perform maintenance, do not let the pool sit empty for too long. In general, throughout the winter it's best to leave water in a pool because the weight of the water counteracts the forces from the ground pressing up against the pool’s bottom.