Master Spas spa filter (4CH-20)

Master Spas

Replacement numbers

Unicel 4CH-20, Pleatco PHC25

Fits Master Spas.

Diameter 4-5/8" (117 mm)Length 6-3/4" (171 mm)20 sq ft

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Unicel4CH-20
PleatcoPHC25 (as printed in the Filbur catalog Master Spas section (printed p.43); not found in the Pleatco 2023 Unicel cross reference)
FilburFC-0125
Topmolded cone handle
Bottom1-1/2” male thread/MPT
Ø 4-5/8" (117 mm)6-3/4" (171 mm)Side view · end views belowTopBottom
Top: molded cone handle
Bottom: 1-1/2” male thread/MPT
Drawn to scale from the listed diameter and length. Handles, threads and closed ends are drawn as symbols, not to scale. 20 sq ft media.

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Master Spas files this cartridge as 4CH-20 cartridge, in the Master Spas group. Numbers on the row: Unicel 4CH-20; Pleatco PHC25; Filbur FC-0125. 4-5/8" across, 6-3/4" long, top molded cone handle, bottom 1-1/2” male thread/MPT, 20 sq ft.

PHC25 is the Pleatco string Filbur prints next to 4CH-20 (OEM 4CH-20 cartridge) on printed p.43. PHC25 itself is absent from Pleatco’s 2023 Unicel cross-reference.

Before ordering 4CH-20, compare it with 4CH-252 differs by Unicel 4CH-252, Pleatco PMA20-F2M, no Filbur number, 8" long, bottom 2” male thread/MPT, 25 sq ft, OEM X268521, note says Unicel: Master Spas original has 4-3/4" OD; and 6CH-352 differs by Unicel 6CH-352, Pleatco PAS40-F2M, Filbur FC-0312, 6" diameter, 8" long, top semi-circular handle, bottom 2” male thread/MPT, 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".

Left blank on purpose: no model/model-year fitment in sources; Unicel lists no OEM part number for this brand entry.

Pages checked for PHC25: Unicel 2026 Replacement Guide on 4CH-20 (OEM cross reference (Master Spas section), PDF p.45 (printed p.41); spec table PDF p.7 (printed p.3)). Filbur Catalog & Reference Guide on 4CH-20 (Product by Pool/Spa Manufacturer (OEM), Master Spas, printed p.43 (PDF p.22)).

If you know the Master Spas model and not the part number, use the Master Spas filter by model and year lookup.

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-20 number is also on the Saratoga Spas page.

Other Master Spas cartridges

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

Sources

Not in sources: no model/model-year fitment in sources; Unicel lists no OEM part number for this brand entry.