The only time that a pool needs to have the water lowered is if you have a gunite or cement pool with tile around the top. If you have a liner in the pool, then there is no need to lower the water level. When you use an air compressor to blow the water out of the pipes, and plug the return jets and skimmers, there is no need to lower the water. As long as you use those big plugs for the skimmers, you can keep the water at the regular level. The higher you can keep the water in the pool, the better it is for your pool cover and there will be much less of a chance of the cover falling in.