Unicel C-4405 Replacement Filter for Rainbow R173502

Overview

The Unicel C-4405 is a pleated polyester spa cartridge filter element providing 25 sq ft of effective filtration area in a compact, threaded-handle configuration engineered for Pentair/Rainbow Dynamic Series spa housings. Dimensional specifications: 4.25-inch OD, 2-1/8-inch ID at the open end, 8-inch length (excluding handle), with a molded ABS top end cap featuring an integral SAE thread for in-housing retention and a closed ABS bottom end cap. Media construction is Reemay nonwoven polyester at nominal 15-micron filtration efficiency, supported on a perforated PVC core for axial rigidity under spa pump operating pressures (typical 5–15 PSI). Maximum continuous service temperature is rated to 115°F, with short-duration excursions to 120°F acceptable. The C-4405 is sold as a single element; full Pentair Dynamic Series filter assemblies typically require a pair (SF / "skim filter" configuration), as reflected in the Pleatco pair-pack reference.

Service interval recommendation for spa applications: fresh-water rinse every 2–4 weeks; chemical soak (dilute TSP or enzyme degreaser) every 4–6 weeks to dissolve body oils, lotions, and surfactant residue that standard rinsing will not displace. Element replacement at 12–15 month intervals under typical residential spa duty, or sooner when ΔP exceeds 5 PSI above clean-filter operating baseline, when pleat channeling is visible, or when fabric degradation is observed at the end cap bond line. Chemical compatibility: polyester media and ABS end caps tolerate continuous service at ≤ 10 ppm free available chlorine or ≤ 30 ppm total bromine; muriatic acid soak at 1:20 dilution is compatible for calcium scale removal (20-minute maximum exposure, thorough rinse before reinstallation). Verify thread engagement and full element seating against the housing standpipe after installation, then confirm clean operating pressure for baseline ΔP reference. Standard Unicel 90-day manufacturer's defect warranty applies through authorized distribution.

What's Included

Your order includes the selected quantity of replacement pool filter cartridges. Each unit is individually inspected for quality before shipping.