Which filter does my Freeflow spa take?

Reviewed November 6, 2026

Look at the top of the old cartridge before you trust the model name. Unicel’s spec table makes TLX and RLX the open-top cartridge 4CH-22 and CLX the closed-top cartridge 4CH-23. Both are 4-15/16" × 6-5/8", 212 pleats, 3 oz, 25 sq ft, with a 1-1/2" MPT bottom. Filbur and Pleatco swap the models: they put CLX on the open cartridge and TLX/RLX on the closed one. The Unicel number’s top style does not swap. 4CH-22 is the open one and 4CH-23 is the closed one in both Unicel’s spec table and Filbur. Legend is a different, longer spa filter, 5-5/16" × 10", open 2-1/8" on top, 1-1/2" MPT, Unicel 5CH-45 at 45 sq ft. Pleatco rates that Legend cartridge at 50 sq ft. Unicel’s model list also puts Passport on 5CH-45. The spec table, Filbur and Pleatco name Legend and do not name Passport.

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The cartridges, with equivalents

Factory part	What it is	Catalog equivalents	Rated area	Our page
No Freeflow part number in Unicel	Open top, 2-1/8". Unicel: TLX and RLX. Filbur and Pleatco: CLX (Pleatco also says Lagas, FF-150).	Unicel 4CH-22. Filbur FC-2399 = Pleatco PFF25P4. Pleatco’s Unicel cross says 4CH-22 = PFF25W-P4 instead.	Unicel and Filbur: 4-15/16" × 6-5/8", 25 sq ft. Pleatco PFF25P4: 4-5/8" × 6-5/8". PFF25W-P4: 5" × 6-5/8".	4CH-22
No Freeflow part number in Unicel	Closed top. Unicel: CLX. Filbur and Pleatco: TLX and RLX (Pleatco also says Lagas, FF-100, Claro).	Unicel 4CH-23; Pleatco PFF25TC-P4; Filbur FC-2400	Unicel and Filbur: 4-15/16" × 6-5/8", 25 sq ft. Pleatco: 4-5/8" × 6-5/8", 25 sq ft.	4CH-23
No Freeflow part number in Unicel	Legend, open 2-1/8" top. Unicel’s model list also names Passport on this row. The other catalogs name Legend only.	Unicel 5CH-45; Pleatco PFF50P4 (Filbur’s cell says PFF50P); Filbur FC-2401	Unicel and Pleatco: 5-5/16" × 10". Filbur’s Freedom section: 5-1/4" × 10". Area 45 sq ft (Unicel, Filbur) or 50 (Pleatco).	5CH-45

The top style and the pleat counts are from Unicel’s spec table. Filbur agrees which Unicel number is open and which is closed, and disagrees which Freeflow model takes which. Pleatco’s own Unicel cross-reference sends 4CH-22 to PFF25W-P4, a 5" cartridge, while Filbur sends 4CH-22 to PFF25P4, the 4-5/8" open cartridge. Those are not the same Pleatco part. FF-150 and FF-100 are printed by Filbur and Pleatco, not by Unicel, so they are not used as OEM lookup numbers on this site.

The short pair: same body, two tops

Unicel’s Freeflow heading lists three model groups and no factory part number. The two short rows are the same outside size. The spec table, not the model list, is where the tops are printed.

	4CH-22	4CH-23
Unicel spec table	4-15/16" × 6-5/8", open 2-1/8", 1-1/2" MPT, 212 pleats, 3 oz, 25 sq ft. Model cell: Freeflow TLX, RLX.	Same size, closed top, 212 pleats, 3 oz, 25 sq ft, 1-1/2" MPT. Model cell: Freeflow CLX.
Unicel Freeflow model list	TLX and RLX	CLX
Filbur dimensional listing	FC-2399, 4-15/16" × 6-5/8", open 2-1/8", 1-1/2" MPT, 25 sq ft. Description: Freeflow 25, CLX. Pleatco cell: PFF25P4.	FC-2400, 4-15/16" × 6-5/8", closed, 1-1/2" MPT, 25 sq ft. Description: Freeflo 25, closed top, TLX. Pleatco cell: PFF25TC-P4.
Filbur Freedom Spas section	CLX, FF-150, PFF25P4, 4CH-22. Filbur files this under the heading Freedom Spas, not under a Freeflow heading.	TLX, RLX, FF-100, closed, PFF25TC-P4, 4CH-23. Same Freedom Spas heading.
Pleatco spec table	PFF25P4: 4-5/8" × 6-5/8", open 2-1/8", 1-1/2" MPT, 3 oz, 25 sq ft. Lagas, CLX, FF-150.	PFF25TC-P4: 4-5/8" × 6-5/8", closed, 1-1/2" MPT, 3 oz, 25 sq ft. Lagas, TLX, RLX, FF-100, Claro.
Pleatco Unicel cross-reference	4CH-22 = PFF25W-P4, not PFF25P4	4CH-23 = PFF25TC-P4

PFF25W-P4 is a third short cartridge. Pleatco’s spec table prints it at 5" × 6-5/8", open 2-1/8", 1-1/2" MPT, 25 sq ft, for Freeflow Lagas, with no TLX, RLX or CLX name. That is the number Pleatco’s cross-reference gives for 4CH-22. It is not the 4-15/16" body Unicel and Filbur print for 4CH-22, and it is not PFF25P4. If the cartridge in your hand is about 5" across rather than just under 5", you are in the PFF25W-P4 row, and neither Unicel’s TLX line nor Filbur’s CLX line has finished the identification.

Filbur has no Freeflow heading. The CLX, TLX, RLX and Legend lines sit in the section titled Freedom Spas. Unicel gives Freeflow its own heading, directly after Freedom Spas, with different model names on the Freedom side. This page does not treat the two headings as one brand. The Freedom Spas lookup is the other list.

A closed top and an open top are not interchangeable, whatever the model badge says. Open-end versus threaded is the fitting check, and how to find your spa filter size is the measuring order. Unicel’s own measuring note excludes handles from the length. Both of these short cartridges are specified at 6-5/8" including the end caps.

Legend, and Passport

Unicel’s spec table prints 5CH-45 as 5-5/16" × 10", open 2-1/8", 1-1/2" MPT, 225 pleats, 3 oz, 45 sq ft, and the model cell says Freeflow Spas Legend. The Freeflow model list puts Legend and Passport on that same 45 sq ft row. Passport is not repeated in the spec-table model cell. Filbur’s dimensional listing prints FC-2401 at 5-5/16" × 10", open 2-1/8", 1-1/2" MPT, 45 sq ft, Pleatco cell PFF50P. Filbur’s Freedom Spas section prints the same FC-2401 at 5-1/4" × 10" for Legend, still at 45 sq ft, still PFF50P. Pleatco’s spec table prints PFF50P4 at 5-5/16" × 10", open 2-1/8", 1-1/2" MPT, 3 oz, 50 sq ft, for Freeflow Spas Legend. The application index names “Spa Freeflow Legend 50.” None of those Pleatco or Filbur lines name Passport.

So a Legend cartridge is the long open one, and the area is 45 or 50 depending on the catalog. A Passport owner has only Unicel’s model list. Measure the old cartridge against 5-5/16" × 10" before ordering 5CH-45, and read both areas on the 5CH-45 page. Why the same body can be given two areas is covered in why same-size filters have different square-foot ratings.

Where the sources disagree

Which model is open. Unicel: TLX and RLX are 4CH-22 (open), CLX is 4CH-23 (closed). Filbur and Pleatco: CLX is the open cartridge, TLX and RLX are the closed one. The Unicel number’s top does not move. The model name does.
Pleatco’s number for 4CH-22. Pleatco’s cross-reference says PFF25W-P4. Filbur says PFF25P4. Pleatco prints those at 5" and 4-5/8", and Unicel prints 4CH-22 at 4-15/16".
Outside diameter of the short pair. Unicel and Filbur 4-15/16". Pleatco PFF25P4 and PFF25TC-P4 4-5/8".
Legend area. Unicel 45 sq ft (225 pleats). Filbur 45 sq ft. Pleatco 50 sq ft.
Legend diameter inside Filbur. Dimensional listing 5-5/16". Freedom Spas section 5-1/4".
Passport. Named only on Unicel’s Freeflow model list, on the 5CH-45 row with Legend.
Lagas, FF-150, FF-100, Claro. Pleatco and Filbur print them. Unicel’s Freeflow heading does not.
The section heading. Filbur files these model names under Freedom Spas. Unicel files them under Freeflow Spas.

How to confirm yours

If the cartridge is about 6-5/8" long, the top decides it. Open 2-1/8" is 4CH-22 / FC-2399. Closed is 4CH-23 / FC-2400 / PFF25TC-P4. Do not pick from “CLX” or “TLX” alone.
If it is about 5" across rather than 4-15/16" or 4-5/8", compare it with Pleatco PFF25W-P4 before you order 4CH-22.
If it is about 10" long and about 5-5/16" across, with an open top and a 1-1/2" MPT bottom, it is the Legend cartridge. Read 45 and 50 sq ft as the two printed areas.
Compare the cartridge with the Freeflow table before ordering. A Freedom model name (Franklin, Statesman, Liberty, Concord) is a different list.

Why one cartridge size can carry two different square-foot ratings: our explainer with Unicel’s pleat-count table.

Sources

This page summarizes published catalogs and dealer fitment tables; always follow your own spa’s owner’s manual. See our disclaimer and methodology.