Chemicals like calcium and oils from bathers can become embedded in the pleats of your pool cartridge filter. These contaminates are difficult to remove with a standard hose cleaning and may have to be removed chemically. If you are having to clean your cartridge filter every 3-4 days to keep the pool pressure down, it may be time to clean your cartridge chemically with a solution like TSP. This guide shows you how to chemically clean your pool's cartridge filter. Although this description is specific to a Hayward cartridge filter, many of the steps can apply to other models of cartridge filters.