Freedom Spas spa filter (C-4637)

Freedom Spas

Replacement numbers

Unicel C-4637, Pleatco PRB37-IN-4

Fits Freedom Spas.

Diameter 4-15/16" (125 mm)Length 13-5/16" (338 mm)37 sq ft1 model listed

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UnicelC-4637
PleatcoPRB37-IN-4 (PRB37-IN-4 is the Pleatco cell in Filbur's Freedom section. Not confirmed in Pleatco's Unicel cross-reference.)
FilburFC-2380
Top2-1/8" (54 mm) / open
Bottom2-1/8" (54 mm) / open
Ø 4-15/16" (125 mm)13-5/16" (338 mm)Side view · end views belowTopBottom
Top: 2-1/8" (54 mm) / open
Bottom: 2-1/8" (54 mm) / open
Drawn to scale from the listed diameter and length and open-end sizes. Handles, threads and closed ends are drawn as symbols, not to scale. 37 sq ft media.

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Freedom Spas files this cartridge as C-4637 cartridge, in the Freedom Spas group. Numbers on the row: Unicel C-4637; Pleatco PRB37-IN-4; Filbur FC-2380. 4-15/16" across, 13-5/16" long, top 2-1/8" / open, bottom 2-1/8" / open, 37 sq ft.

PRB37-IN-4 carries this note from the catalogs: Unicel's Freedom list names Concord, Patriot, Ambassador and Executive on this row only: 4-15/16" x 13-5/16", C-4637, 37 sq ft, 4 oz. The spec table gives 158 pleats, 2-1/8" open ends, and calls 37 sq ft an upgrade of the 25 sq ft C-4326 and C-4625. The brands on that spec line are Rainbow, Waterway, Morgan, Leisure Bay and Custom Molded Products, not Freedom. Filbur's Freedom section calls FC-2380 Rainbow Dynamic 37 and does not print the Concord names. PRB37-IN-4 is Filbur's Pleatco cell.

C-4637 (OEM C-4637 cartridge), Pleatco side: PRB37-IN-4 is the Pleatco cell in Filbur's Freedom section. Not confirmed in Pleatco's Unicel cross-reference..

PRB37-IN-4, Filbur note: Freedom Spas section PDF p.18 (printed p.35): FC-2380, 4-15/16" x 13-5/16", open, Rainbow Dynamic 37, PRB37-IN-4, C-4637, 37 sq ft..

Model list attached to C-4637 cartridge: Concord, Patriot, Ambassador and Executive, no year range printed, listed by Unicel 2026 Replacement Guide (Unicel Freedom list only. Filbur's matching row says Rainbow Dynamic 37.).

C-4637 is easy to confuse on the Freedom Spas table. 4CH-30 differs by Unicel 4CH-30, Pleatco PTL25P-4, Filbur FC-0141, 4-5/8" diameter, 11-7/8" long, top molded cone handle, bottom 1-1/2” male thread/MPT, 30 sq ft, note says Shown at 30 sq ft because that is Unicel's Freedom Spas line, Unicel's spec table (158 pleats, 4 oz), Filbur's size table and Aladdin 13005. Unicel's Sundance line prints the same 4CH-30 for OEM 6540-484 at 25 sq ft, and Filbur's Sundance line does too. Unicel names Franklin, Statesman and Revere. Aladdin's model field uses that same string and lists Freedom among many brands, including Dimension One and Sundance. Pleatco's Unicel cross-reference does not list 4CH-30; PTL25P-4 is Filbur's Pleatco cell.. 6CH-45 differs by Unicel 6CH-45, Pleatco PTL45W-P-4, Filbur FC-0330, 6" diameter, 12-3/8" long, top semi-circular handle, bottom 1-1/2” male thread/MPT, 45 sq ft, note says Length is Unicel's 12-3/8", which Aladdin 14506 also prints. Filbur's size table and Freedom Spas section print FC-0330 at 12-1/4". Unicel names Statesman, Lexington, Enterprise, Aristocrat and Franklin. Aladdin's model field matches that string and names Freedom Spas and Master Spas. Pleatco's number here is Filbur's cell (PTL45W-P-4); Aladdin prints PTL45W-P4-4..

Left blank on purpose: Concord, Patriot, Ambassador and Executive are Unicel's Freedom list only. Spec-table applications and Filbur do not use those names. The following C-4950 row, not this one, carries the 1993 note. No Freedom OEM number..

Pages checked for PRB37-IN-4: Unicel 2026 Replacement Guide on C-4637 (Freedom Spas line, PDF p.35 (printed p.31): Concord, Patriot, Ambassador, Executive = C-4637, 37 sq ft; spec table PDF p.9 (printed p.5): 158 pleats, 2-1/8" open, upgrade of C-4326 and C-4625, application line does not name Freedom). Filbur Catalog & Reference Guide on C-4637 (Freedom Spas section PDF p.18 (printed p.35): FC-2380, Rainbow Dynamic 37, PRB37-IN-4, C-4637, 37 sq ft. No Concord names).

Hot tubs listed for this cartridge

The rest of the Freedom Spas model list is the Freedom Spas filter by model and year lookup.

Model / systemYearsListed by
Concord, Patriot, Ambassador and Executive (Unicel Freedom list only. Filbur's matching row says Rainbow Dynamic 37.)not givenUnicel 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. Number formats: how Filbur, Unicel and Pleatco numbers compare.

Other Freedom Spas cartridges

All 6 Freedom 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: Concord, Patriot, Ambassador and Executive are Unicel's Freedom list only. Spec-table applications and Filbur do not use those names. The following C-4950 row, not this one, carries the 1993 note. No Freedom OEM number..