Listing we opened and checked. Match the diameter, length and both fittings on this page before you order. The price is on Amazon; we do not print one.
Master Spas OEM X268521 spa filter (4CH-252)
Master Spas Contractor Series 415 / Clarity Spas 415
Replacement numbers
Unicel 4CH-252, Pleatco PMA20-F2M
Fits Master Spas OEM X268521.
Diameter 4-5/8" (117 mm)Length 8" (203 mm)25 sq ft2 models listedPleatco PMA20-F2M
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| Unicel | 4CH-252 |
|---|---|
| Pleatco | PMA20-F2M |
| Filbur | not found in Filbur catalog |
| Top | molded cone handle |
| Bottom | 2” male thread/MPT |
Bottom: 2” male thread/MPT
Drawn to scale from the listed diameter and length. Handles, threads and closed ends are drawn as symbols, not to scale. 25 sq ft media.
Master Spas Contractor Series 415 / Clarity Spas 415 is the group name on the Master Spas row 4CH-252 cartridge (OEM X268521). Match these numbers: OEM X268521; Unicel 4CH-252; Pleatco PMA20-F2M. 4-5/8" across, 8" long, top molded cone handle, bottom 2” male thread/MPT, 25 sq ft.
Catalog note for X268521: Unicel: Master Spas original has 4-3/4" OD.
Hot tubs named for X268521: Contractor Series 415, no year range printed, listed by Unicel 2026 Replacement Guide; Clarity Spas 415, no year range printed, listed by Unicel 2026 Replacement Guide.
4CH-252 is easy to confuse on the Master Spas table. 6CH-352 differs by Unicel 6CH-352, Pleatco PAS40-F2M, Filbur FC-0312, 6" diameter, top semi-circular handle, 35 sq ft, OEM PMA-R1, note says Unicel: must remove black stand pipe. Filbur cross-references 6CH-352 to FC-0312 but lists FC-0312 at 6" x 7". 6CH-940 differs by Unicel 6CH-940, Pleatco PWW50P3, Filbur FC-0359, 6" diameter, 8-1/4" long, top semi-circular handle, bottom injection molded 1-1/2" SAE thread, 45 sq ft, no OEM number, note says Unicel: for use in Master Spas swim spas.
Filbur does not have a number on this row. Search X268521 or the Master Spas part you pulled out of the spa.
Left blank on purpose: no Filbur equivalent found in Filbur catalog.
Where those figures are printed: Unicel 2026 Replacement Guide on 4CH-252 (OEM cross reference (Master Spas section), PDF p.45 (printed p.41); spec table PDF p.7 (printed p.3)). Pleatco 2023 Catalog on 4CH-252 (Unicel-to-Pleatco cross reference, PDF p.47).
Hot tubs listed for this cartridge
The rest of the Master Spas model list is the Master Spas filter by model and year lookup.
| Model / system | Years | Listed by |
|---|---|---|
| Contractor Series 415 | not given | Unicel 2026 Replacement Guide |
| Clarity Spas 415 | not given | Unicel 2026 Replacement Guide |
Check the cartridge you removed
Measure diameter, length, and both ends, then compare them with the figures above. The steps are in the measuring guide. Why the bottom decides whether it seals: open-end vs threaded filters. Power, the retainer, and not running the spa empty: how to install a cartridge. Brand notes: Master Spas Eco-Pur filters. Number formats: how Filbur, Unicel and Pleatco numbers compare.
The same 4CH-252 number is also on the Cal Spas, Coleman Spas pages.
Other Master Spas cartridges
- 6CH-352 cartridge (OEM PMA-R1), 6" (152 mm) × 8" (203 mm)
- 6CH-940 cartridge, 6" (152 mm) × 8-1/4" (210 mm)
- 4CH-949 cartridge, 4-15/16" (125 mm) × 13-1/2" (343 mm)
- 6CH-402 cartridge (OEM PMA40L-F2M), 6" (152 mm) × 9-1/2" (241 mm)
- 7CH-322 cartridge, 7" (178 mm) × 8" (203 mm)
- C-7330 cartridge, 7" (178 mm) × 7-1/4" (184 mm)
All 13 Master Spas spa filters
Every number on this row, on one screen: cross-reference lookup. Published clean and replace intervals for this cartridge, and a buy link for the numbers above: replacement schedule and reorder. The interval comparison by brand: calculator.
Cleaner and test strips
Hose rinse and soak steps are in how to clean a cartridge. Named cleaners and strips are in filter cleaners and test strips.
Filter cleaner and test strips
-
Leisure Time O Filter Clean Cartridge Cleaner Listing title: cartridge cleaner, 32 fl oz.
-
SpaGuard Filter Cleaner Listing title: filter cleaner for spas and hot tubs, 1 quart.
-
AquaChek SPA 6-in-1 Test Strips Listing title: reads total bromine, total chlorine, free chlorine, pH, total alkalinity and total hardness.
Pleatco PMA20-F2M Listing we opened and checked. Match the diameter, length and both fittings on this page before you order. The price is on Amazon; we do not print one.
Sources
- Unicel 2026 Replacement Guide: OEM cross reference (Master Spas section), PDF p.45 (printed p.41); spec table PDF p.7 (printed p.3) (PDF)
- Pleatco 2023 Catalog: Unicel-to-Pleatco cross reference, PDF p.47 (PDF)
Not in sources: no Filbur equivalent found in Filbur catalog.