There are 3 types of pool filters – Sand, DE and Cartridge. Keeping these filters maintained will keep your pool clean. Backwash Sand filters every 4-6 weeks and change the sand every 5 years. Backwash DE filters quarterly and clean and inspect the grids and manifold yearly. Clean and inspect Cartridge filters every 6 months and replace the cartridges every 3-4 years or as needed. Don’t forget to make sure the pressure gauge is in good, working condition!