Unicel C-4401 Replacement Filter for Rainbow R173500

Overview

The Unicel C-4401 is a pleated polyester spa cartridge filter element engineered for residential spa and portable hot tub applications, delivering 17.5 sq ft of effective filtration area through a nonwoven polyester media pack at a nominal 15-micron filtration efficiency. Dimensional specifications: 4.25-inch OD, 2.125-inch ID, 8.25-inch length, with a Super-Flo (SAE thread) bottom adapter and an open-flow top end cap. End cap construction is ABS injection-molded with UV-stabilized adhesive bond; coreless pleat geometry is supported by the molded thread base for axial rigidity under standard spa circulation loads. Maximum continuous operating temperature is 115°F with intermittent excursion capability to 120°F; rated for spa circulation pressures up to 15 PSI. The threaded-base configuration provides positive mechanical engagement to compatible standpipe manifolds, eliminating bypass risk associated with friction-fit seating.

Service interval recommendation for spa applications: rinse with fresh water every 2–4 weeks; chemical soak (dilute TSP or commercial enzyme cleaner) every 4–6 weeks to dislodge oils, lotions, and surfactant residue that resist water-only rinsing. Replacement criteria: ΔP ≥ 5 PSI above clean-filter baseline, visible pleat damage, thread deformation at the base adapter, or 12 months service maximum — whichever occurs first. Daily-use spa installations typically require replacement at 6-month intervals. Chemical compatibility: polyester fabric is rated for 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, rinse thoroughly before reinstallation). Enzyme cleaners compatible without restriction. Standard Unicel 90-day manufacturer's defect warranty applies through authorized distribution channels.

What's Included

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