Which Darlly cartridge fits my Hot Spring (Watkins) filter?

Find your filter model in the table above. The Darlly column is the replacement cartridge, and "Per filter" is how many to order for a full set. You can also search any Hot Spring (Watkins) cartridge number in the box above.

What if my filter is not listed?

Search the part number printed on your old cartridge, or measure its outside diameter and length and use the measurement search. Darlly makes over 600 cartridge sizes.

Hot Spring (Watkins) Filter Cartridges: Darlly Replacements

Darlly replacement cartridges for 6 Hot Spring (Watkins) filter models. Each row shows the filter, how many cartridges it takes, the OEM cartridge number, the Darlly part, and the Unicel, Pleatco and Filbur equivalents.

Filter	Darlly	Per filter	Size	OEM cartridge	Unicel	Pleatco	Filbur
Watkins, Freedom Spa (303279)	50406	1	5-3/8" x 9-1/2"	303279		PFF42TC-P4
Hot Spring 30 sq ft	60301	1	6" x 10-1/2"	31489	C-6430 (discontinued)	PWK30 (now ULTRA-S12)	FC-3915
Hot Springs Spas/Watkins Mfg	60307	1	6" x 10-1/2"		C-6330	PWK30 (now ULTRA-S12)
Watkins / Hot Spring Limelight series, 2018 and later	60511	1
Watkins # 78373 - 50 SF Pleated Cartridge	60512	1	6-3/8" x 14"
Hot Spring 65 sq ft (upgrade from PWK45N)	80651	1	8-1/2" x 10-1/2"	31114	C-8465	PWK65, ULTRA-S16	FC-3960

Other brands

Hayward29 filters Pentair26 filters Jandy10 filters Sta-Rite15 filters Waterway23 filters Rainbow6 filters Intex, Aqua Leisure and Coleco2 filters Sundance Spas6 filters Jacuzzi5 filters Caldera Spas3 filters Bullfrog Spas4 filters Artesian Spas4 filters Cal Spas3 filters Marquis Spas2 filters Rec Warehouse and Leisure Bay3 filters Freeflow Spas2 filters Spa top-load and skimmer cartridges9 filters D.E. filter grids5 filters PureStream prefilters4 filters

Questions

Which Darlly cartridge fits my Hot Spring (Watkins) filter?: Find your filter model in the table above. The Darlly column is the replacement cartridge, and "Per filter" is how many to order for a full set. You can also search any Hot Spring (Watkins) cartridge number in the box above.
What if my filter is not listed?: Search the part number printed on your old cartridge, or measure its outside diameter and length and use the measurement search. Darlly makes over 600 cartridge sizes.

Where to buy Darlly cartridges

Pool and spa businesses in Florida, Georgia, South Carolina, Alabama, Mississippi, Louisiana and Texas order through their Grit Game rep. Everywhere else, contact Darlly Filtration directly.

Find your Grit Game rep Contact Darlly

Cross-reference checked October 21, 2026 against Unicel's 2026 Replacement Guide, Pleatco's catalog (updated September 2025), filbur.com and darllyfilter.com. A competitor number is listed only when that brand's own data pairs it with the same cartridge size. Always compare the size and end caps of your old cartridge before ordering.

Brand names and part numbers are trademarks of their respective owners and are shown only to identify compatible replacements. Darlly Filtration is not affiliated with or endorsed by them. Cross-reference by The Grit Game, Darlly's sales agency.