Unicel® C-5345 – 45 Sq Ft Rainbow/Waterway Spa Filter Cartridge – part #C-5345
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Key Features & Benefits
Universal Replacement Cartridge
Fits Rainbow, Waterway, and other spas using a 45 sq ft, 2-1/8" open-end cartridge.
Reemay® Polyester Media
Engineered for seamless compatibility with original mounting points for secure placement.Spunbond polyester construction captures fine particles, body oils, and debris.
Cross-Reference Compatible
Direct equivalent to Waterway 817-0045P, Rainbow R173445, Pleatco PRB45-IN, and Filbur FC-2390.
Open Top & Bottom Design
2-1/8" inner diameter fits standard spa filter housings without adapters.
Reusable With Regular Cleaning
Rinse weekly and deep-clean monthly with a filter cleaner to extend service life.
Works With Any Sanitizer System
Mechanical filtration performs the same with chlorine, bromine, saltwater, or mineral systems.
Product Overview
The Unicel® C-5345 is a 45 square foot replacement filter cartridge built for Rainbow, Waterway, and other spa systems specifying a cartridge of this size and open-ended design. It's a widely cross-referenced part, directly equivalent to Waterway 817-0045P, Rainbow R173445, Pleatco PRB45-IN, and Filbur FC-2390 — so it's a safe substitute if your spa currently uses any of those cartridges.
The cartridge is built from Reemay® spunbond polyester media, pleated to maximize surface area for capturing fine particles, body oils, and everyday debris without restricting water flow. It measures 5-5/16" in outer diameter and 10-1/8" in length, with open top and bottom ends and a 2-1/8" inner diameter that fits standard spa filter housings without adapters. As a mechanical filter, it performs the same regardless of sanitizer type — chlorine, bromine, saltwater, and mineral systems all filter through it identically.
To keep it working effectively, rinse the cartridge weekly with a garden hose and soak it in a filter cleaner solution about once a month to break down oils and lotions that a plain rinse won't remove. Inspect the pleats periodically for tears or sagging, and plan to replace the cartridge roughly every 12 months — sooner in heavily used spas or if water quality starts to suffer between cleanings.
Frequently Asked Questions
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Fits Rainbow, Waterway, and compatible systems using a 45 sq ft, open-ended cartridge — verify dimensions to confirm fit.
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Yes, rinse weekly and use a filter cleaner monthly to prolong its lifespan.
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Typically once a year, or sooner in high-use spas or poor water conditions.
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Yes, it is an equivalent replacement made with Reemay® filter media.
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Yes — as a mechanical filter cartridge, it filters the same regardless of sanitizer type, including saltwater and mineral systems.