To winterize a swimming pool, remove all debris, keep algae out with a phosphate remover and test the chemicals. It is also important to manage the water level prior to freezing temperatures.
Winterizing should begin about a week before the pool plans to close for the winter season. This is when the phosphate remover is added to keep out algae throughout the cold season. Clean the pool before closing it by using a brush and vacuum to remove debris and any existing algae. Also shock the pool, which helps to kill bacteria so it doesn’t linger the entire winter. Also add more chlorine as needed when winterizing a pool.
If the location of the pool doesn’t get to freezing temperatures in the winter, the water level needs to be filled to the top, where it is practically overflowing. For areas with freezing temperatures from snow and ice, keep it about 4 to 6 inches below the top level. After getting the pool to the right water level, use a test kit to measure and balance the water chemistry. The goal is to have alkalinity between 80-120 ppm and pH between 7.4 and 7.6.
As the last winterizing steps, backwash the filter, drain the pool lines and add antifreeze if the pool is in a freezing temperature location.