The Unicel 5CH-37 delivers 37.5 square feet of filtration across 221 pleats of Reemay® polyester media, capturing debris down to an average of 20 microns. Built to meet or exceed OEM specifications, it’s the replacement cartridge for select Aquaterra® and Hot Spring® spas, taking the place of Watkins part 303279.
Filtration is the quiet backbone of clean spa water. Every soak leaves behind body oils, lotions, hair, and fine debris, and the cartridge is what removes all of it before it clouds the water, feeds bacteria, or coats your plumbing. When a filter is worn or clogged, the effects spread everywhere: dull water, higher chemical use, softer jets, and a pump and heater straining against restricted flow.
What separates a Unicel from a bargain cartridge is the media itself. Reemay uses a trilobal fiber — three-lobed in cross-section rather than round — which delivers roughly 45% more surface area than standard rounded filter fibers. More surface means more places to capture dirt and oils, higher dirt-holding capacity, and more time between cleanings. Add a bar handle on top for easy lifting, a 1-1/2 inch male pipe thread bottom that screws in for a tight seal, and chemical-resistant end caps, and you get a cartridge built to last. Made in the USA.
Pro Tip: Unicel’s 5-series cartridges look alike — the top style is what tells them apart. All three share a 1-1/2 inch MPT bottom, but they are not interchangeable: the 5CH-35 is 8 inches tall with a semi-circular handle, the 5CH-37 is 9 inches tall with a bar handle, and the 5CH-45 is 10 inches tall with an open top. Look at the top of your current cartridge and check its length before ordering.
Brand
UNICEL®
