If you own an in-ground swimming pool and live in a climate where freezing temperatures are normal, you'll need to winterize your pool to protect it during cold-weather months. This will protect it from damage due to freezing water and keep it as clean as possible for the next season.
Check Your Chemistry
The first step in the winterization procedure is to make sure your water chemistry is balanced, including the pool's pH, total alkalinity, and calcium hardness. Doing this will protect the edge of the pool from staining and etching. Adding a winterizing chemical kit to your water will help keep it blue and clear for the next season. Be sure to follow the manufacturer's instructions for the kit. Do not use a floater that contains a strong oxidizer (chlorine or bromine) because the floater may stick against the pool wall and stain or bleach it.
Protect the Skimmer
When water freezes, it expands. This can cause great damage to your pool, pool plumbing, and its filter system. To avoid this, lower the water below the mouth of your skimmer(s). This will get the water out of the throat of the skimmer which can be easily damaged if water were to freeze there.