Covering your pool is the smartest way for peace of mind while the pool is closed.  Closing your pool protects against costly freezing conditions.  It gives you peace of mind if you lose power, travel or can't keep up during the off season. The closing process consists of blowing water out and closing off the lines, filling skimmers and water features with marine grade biodegradable antifreeze, chemically treating the water, pulling all plugs on equipment and covering the pool.  It is possible to close pools without covers but it is difficult to keep them clean during off season.  Covers keep children, pets and leaves out of the pool.