Tier1 Replacement for FCH-22 Freeflow Lagas CLX, Pleatco PFF25W-P4, Filbur FC-2399, Unicel 4CH-22 Filter Cartridge Replace your filter when the pressure gauge on your filter tank reaches 8 psi above the pressure recorded when first installed. Turn off the power to your pump and bleed the excess air pressure of the system using the air valve on the filter. Remove any band clamps and/or lids to your filter. Remove the cartridge from the filter canister and dislodge any loose debris Rinse the cartridge thoroughly with clean fresh water and return it to the filter tank. Secure the tank lid and any band clamps.