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 you are installing a new DE filter, you will have to coat the new DE grids with a layer DE Filter Powder. If you have backwashed an operational DE Filter to clean the grids, you will have to recoat the grids with a layer of new DE Powder. This guide shows you how to add or replace DE Filter Powder in your DE Filter.