Proper winterizing is a key aspect of pool maintenance. The dropping temperatures and harsh weather conditions can wreck havoc on a pool that is not properly prepared. In particular, water that freezes can inflict significant structural and cosmetic damage to a pool that has not been winterized correctly. Before closing your pool for the season, familiarize yourself with the problems that can occur so you know how to prevent them.
Cracked Tile
In a tile-lined pool, frozen water can do a great deal of damage. While many types of pool tile are treated to resist chipping from ice damage, surface water that freezes may expand enough to crack the entire tile. As a result, a tile-lined pool should be drained slightly when preparing it for the winter so the water line falls beneath the tile design. If the water line is lowered, the tile is protected should freezing occur.

Broken Skimmers and Filter
The skimmers and filter that are used to keep your pool clean during the summer season are typically made of plastic. If they are left in the pool during the winter and the water freezes, the expansion inside the skimmers and filter can push against their walls and cause them to crack. If your skimmers and filter are removable, take them out of the pool before covering it for the winter. For items that cannot be removed, lower the waterline beneath them so they are protected should the pool water freeze. You may also purchase a skimmer plug, which is expandable and helps prevent the skimmer from cracking.

Torn Vinyl Liner
Vinyl lined pools require special protection from frozen water. If a vinyl liner has a leak, the pool may lose several inches of water over the course of a winter. As the pool loses water, any ice that forms on the surface of the water may begin to fall. If the sheet of ice is thick enough, it can tear the liner. Prior to closing your vinyl-lined pool, inspect for possible leaks. If you suspect a leak, patch it. In the event that you cannot patch the liner before the winter, remember to periodically add water to the pool over the course of the winter to prevent ice sheets from falling.

Burst Pipes
The most serious damage that can occur to a pool due to frozen water is a burst pipe. If water is left inside the pipes during the winter, it can freeze and expand so it pushes against the interior of the pipes and causes them to burst. When winterizing your pool, drain the pipes. Use a compressor or high power vacuum connected to the return lines at the filter to blow out the entire system. You can also add anti-freeze to the pipes to prevent freezing and bursting.