Tier1 Replacement for Waterway 817-4035, Teleweir 35 SF, Pleatco PWW35L, Unicel 4CH-935 Antimicrobial Spa Filter Cartridge AFFORDABLE REPLACEMENT: Replacement 817-4035 filter for 35 sq ft Pool and Spa systems that need 5 inch (Outside diameter) by 8 1/2 inch (Length) filters INCREDIBLY SIMPLE TO USE: Easily replace your old Pleatco PWW35L cartridge with your Tier1 817-4035 EXTREMELY DURABLE: Durable and Washable Pleated fabric that maintains strength even when loaded with sediment, our high flow core is designed to support the filter while providing industry leading flow rates while causing less wear and tear on your pump SPA FILTER CARTRIDGE REPLACEMENT: This Tier1 817-4035 can be used in place of your Unicell 4CH 935. 100% TIER1 NO WORRIES GUARANTEE: We stand behind the quality of filtration and overall performance of our Tier1 filters! 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.