Where you live determines whether or not you should winterize your pool. If your location experiences temperatures that drop below freezing, you'll need to take steps to ensure that your pool stays healthy. Residual pool water left in pipes can freeze and cause damage. To prevent this from happening, use an air compressor to blow water out of the pool's plumbing when swimming season is over. Also, drain as much water as possible from the filter and heater. Any remaining water can be eliminated using nontoxic antifreeze (caution: this is different from antifreeze for vehicles). Disconnect the heater, pump and chemical feeders, the latter of which should be cleaned and stored.
Finally, clean the pool: skim, brush walls, vacuum, empty skimmer baskets, close skimmer line valve, lower water level to approximately 18 inches (45 centimeters) below the coping and supercholorinate. Lastly, cover the pool to keep out debris.