4-5/8" × 6-3/4"
Master Spas spa filters
Master Spas tubs fall into two groups: threaded top-load cartridges, and the Eco-Pur systems that pair an outer micro filter with a small inner cartridge. Unicel dates the Eco-Pur outer cartridges to 2002–2005 and 2006 onward, and several of its Eco-Pur replacements require removing a black stand pipe.
If your cartridge has no OEM number, match it on diameter, length and the bottom thread (male MPT vs. female SAE).
This page lists 13 Master Spas replacement cartridges from the Unicel 2026 Replacement Guide, the Pleatco 2023 catalog and the Filbur catalog, plus model and model-year fitment for 5 of them (5 hot tub models in total). 10 have a Filbur number. Find your spa filter by the OEM part number on the end cap, or measure it and compare sizes below.
Clean and replace intervals for one cartridge on this list, plus the cross-reference numbers and a buy link: filter replacement schedule and reorder.
- 4CH-204CH-20, 4-5/8" (117 mm) × 6-3/4" (171 mm)See replacement
- X2685214CH-252, 4-5/8" (117 mm) × 8" (203 mm)See replacement
- 4CH-9354CH-935, 4-15/16" (125 mm) × 9-1/4" (235 mm)See replacement
- 4CH-9494CH-949, 4-15/16" (125 mm) × 13-1/2" (343 mm)See replacement
- PMA-R16CH-352, 6" (152 mm) × 8" (203 mm)See replacement
- PMA40L-F2M6CH-402, 6" (152 mm) × 9-1/2" (241 mm)See replacement
- 6CH-456CH-45, 6" (152 mm) × 12-3/8" (314 mm)See replacement
- 6CH-9406CH-940, 6" (152 mm) × 8-1/4" (210 mm)See replacement
- 7CH-3227CH-322, 7" (178 mm) × 8" (203 mm)See replacement
- 8CH-668CH-66, 8" (203 mm) × 9-1/4" (235 mm)See replacement
- C-3310AMC-3310AM, 3-7/8" (98 mm) × 7" (178 mm)See replacement
- C-7330C-7330, 7" (178 mm) × 7-1/4" (184 mm)See replacement
- C-8341C-8341, 8" (203 mm) × 6-3/4" (171 mm)See replacement
| Cartridge | Unicel | Pleatco | Filbur | Size | Fits | Status |
|---|---|---|---|---|---|---|
| 4CH-20 (Master Spas) | 4CH-20 | PHC25 | FC-0125 | 4-5/8" (117 mm) × 6-3/4" (171 mm), 20 sq ft | not listed | verified |
| X268521 | 4CH-252 | PMA20-F2M | not listed | 4-5/8" (117 mm) × 8" (203 mm), 25 sq ft | 2 models | verified |
| 4CH-935 (Master Spas Eco-Pur (5" OD)) | 4CH-935 | PWW35L | not listed | 4-15/16" (125 mm) × 9-1/4" (235 mm), 35 sq ft | not listed | verified |
| 4CH-949 (Master Spas Eco-Pur (5" OD)) | 4CH-949 | PWW50L | FC-0172 | 4-15/16" (125 mm) × 13-1/2" (343 mm), 50 sq ft | not listed | verified |
| PMA-R1 | 6CH-352 | PAS40-F2M | FC-0312 | 6" (152 mm) × 8" (203 mm), 35 sq ft | not listed | verified |
| PMA40L-F2M | 6CH-402 | PMA40L-F2M | FC-0317 | 6" (152 mm) × 9-1/2" (241 mm), 40 sq ft | 1 model | verified |
| 6CH-45 (Master Spas) | 6CH-45 | PTL45W-P-4 | FC-0330 | 6" (152 mm) × 12-3/8" (314 mm), 45 sq ft | not listed | verified |
| 6CH-940 (Master Spas swim spas) | 6CH-940 | PWW50P3 | FC-0359 | 6" (152 mm) × 8-1/4" (210 mm), 45 sq ft | 1 model | verified |
| 7CH-322 (Master Spas Eco-Pur (7"/8" OD)) | 7CH-322 | PAS35-F2M | FC-0420 | 7" (178 mm) × 8" (203 mm), 32 sq ft | not listed | verified |
| 8CH-66 (Master Spas) | 8CH-66 | PMA60-F2M | FC-0515 | 8" (203 mm) × 9-1/4" (235 mm), 60 sq ft | not listed | verified |
| C-3310AM (Master Spas Eco-Pur (inner)) | C-3310AM | PMA10 | not listed | 3-7/8" (98 mm) × 7" (178 mm), 8 sq ft | not listed | verified |
| C-7330 (Master Spas Eco-Pur Micro Filter (2002-2005)) | C-7330 | PMA30-2002-R | FC-1003 | 7" (178 mm) × 7-1/4" (184 mm), 30 sq ft | 1 model | verified |
| C-8341 (Master Spas Eco-Pur Micro Filter (2006-present)) | C-8341 | PMA45-2004-R | FC-1007 | 8" (203 mm) × 6-3/4" (171 mm), 40 sq ft | 1 model | verified |
Know your model but not the part number? See Master Spas filter by model and year.
5 of these rows do not have enough detail for a stand-alone page (for example, no OEM number or no second cross-reference), so their pages are kept out of search results and this table is the main reference for them.
Brands that share cartridges with Master Spas
- Waterway Plastics, same part numbers 4CH-935, 4CH-949, 6CH-940
- Coleman Spas, same part numbers 4CH-252, 7CH-322
- Bullfrog, same part number 6CH-940
- Cal Spas, same part number 4CH-252
- Freedom Spas, same part number 6CH-45
Guides that apply to Master Spas
- Master Spas Eco-Pur filters
- Spas that hold more than one cartridge
- Open-end vs threaded hot tub filters
- How Filbur, Unicel and Pleatco numbers compare
- How to find your spa filter size
- How to install a cartridge
- All guides
Search Master Spas part numbers on Amazon
Each button opens an Amazon search for that part number. The cartridge page is where the cited size and fittings are. Match those before you buy.
Part numbers from this table
-
4CH-20 cartridge -
4CH-252 cartridge (OEM X268521) 4-5/8" × 8"
-
4CH-935 cartridge 4-15/16" × 9-1/4"
-
4CH-949 cartridge 4-15/16" × 13-1/2"
Disclosure: we may earn a commission from qualifying purchases made through retailer links on this site, at no extra cost to you. As an Amazon Associate I earn from qualifying purchases. Amazon links on this page go to Amazon.com and are affiliate links; they never change what we write, and the list is not ranked by commission. Each “Search on Amazon” button opens an Amazon search for the part or product name shown, not a single listing we pre-checked. Check size, quantity and your spa maker’s guidance before you buy. See our affiliate disclosure.
Model-year fitment comes only from the sources named on each cartridge page. Where no source lists models or years, the page says so.