Tier1 Replacement for Watkins 31489, Pleatco PWK30, Filbur FC-3915, Unicel C-6430 Antimicrobial Pool and Spa Filter for Watkins Spas AFFORDABLE REPLACEMENT: Replacement 31489 filter for 30 sq ft Watkins Spa and any systems that need 5 7/8 inch (Outside diameter) by 10 1/2 inch (Length) filters INCREDIBLY SIMPLE TO USE: Easily replace your old C-6430, PWK30, FC-3915 filter with the Tier1 31489 filter 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. FITS THE MODEL NUMBERS: This Tier1 13489 filter can be used to replace your C-6430 hot tub filter. 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.