Unicel 5CH-37 Hot Tub Filter for Aquaterra Spas

The Unicel 5CH-37 is a premium replacement filter used in select Aquaterra Spas and Watkins Hot Springs Spas models that require the OEM 303279 filter. Because both Watkins and Aquaterra have used different-sized filters across their spa models over time, it’s important to confirm this cartridge’s dimensions match your existing filter before ordering to ensure the correct fit.

Specifications:

• Part Number: 5CH-37

• Diameter: 5-5/16"

• Length: 9"

• Top: Handle

• Bottom: 1-1/2" MPT Thread

• Media Area: 37.5 sq. ft.

• Filter Media: 3 oz. Reemay® premium trilobal fabric

• Pleat Count: 221

Compatible Replacements:

• Watkins 303279

• Pleatco PFF42TC-P4

• ProAqua PA-537

• Filbur FC-2402

Extended Lifespan:
While most spa filters require replacement every 6–12 months, the Unicel 5CH-37 is built with Reemay® premium trilobal filtration media, providing 45% more surface area than standard rounded fibers. With proper maintenance and cleaning, it can last up to two years or more, depending on usage and care routine.