A Diatomaceous Earth (DE) Filter cleans your pool water by passing the water through a set of normally 8 grids. Each of these grids is covered with a layer of DE powder. If your pools water is not clear and/or your filter's pressure gauge is reading about 10 psi higher than normal, It's time to backwash your filter to strip the current layer of DE power off the grids and replace it with new powder. Although this guide is specific to a Hayward Pro Grid DE Filter, many of its steps are applicable to most DE filters. Note: About once a year you should take the grids out of your DE Filter and clean them more thoroughly. See our guide on "How To Remove and Clean Hayward DE Filter Grids" for more information.