Dimension One Spas OEM 1561-05 spa filter (4CH-50)

Dimension One Spas

Replacement numbers

Unicel 4CH-50, Pleatco PTL50P-4

Fits Dimension One Spas OEM 1561-05.

Diameter 4-5/8" (117 mm)Length 14-3/4" (375 mm)50 sq ft3 models listed

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Unicel4CH-50
PleatcoPTL50P-4 (as printed in the Filbur catalog Dimension One Spas section (printed p.33); not found in the Pleatco 2023 Unicel cross reference)
FilburFC-0151
Topmolded cone handle
Bottom1-1/2” male thread/MPT
Ø 4-5/8" (117 mm)14-3/4" (375 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. 50 sq ft media.

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Dimension One Spas files this cartridge as 4CH-50 cartridge (OEM 1561-05), in the Dimension One Spas group. Numbers on the row: OEM 1561-05; Unicel 4CH-50; Pleatco PTL50P-4; Filbur FC-0151. 4-5/8" across, 14-3/4" long, top molded cone handle, bottom 1-1/2” male thread/MPT, 50 sq ft.

PTL50P-4 is the Pleatco string Filbur prints next to 4CH-50 (OEM 1561-05) on printed p.33. PTL50P-4 itself is absent from Pleatco’s 2023 Unicel cross-reference.

Model list attached to 4CH-50 cartridge (OEM 1561-05): Dimension One Legend, Californian, Ambassador, Chancellor, years 1991, listed by Hot Tub Outpost OEM listing; Dimension One Californian, Challenger, Legend 1500 Series, years 1992, listed by Hot Tub Outpost OEM listing; Dimension One Arena, years 1993, listed by Hot Tub Outpost OEM listing.

4CH-50 is easy to confuse on the Dimension One Spas table. 4CH-940 differs by Unicel 4CH-940, Pleatco PDO-UF40P2, Filbur FC-0177, 15" long, top semi-circular handle, bottom 1-1/4" SAE thread, 40 sq ft, OEM 1561-13. 4CH-950 differs by Unicel 4CH-950, Pleatco PDO-UF25P2, Filbur FC-0173, 12" long, top semi-circular handle, bottom 1-1/4" SAE thread, 25 sq ft, OEM 1561-04, note says Unicel gives the length as 12"; Filbur's table prints 11-7/8" (and "4-5/8 x 12" in its description) for FC-0173..

Pages checked for 1561-05: Unicel 2026 Replacement Guide on 4CH-50 (OEM cross reference (Dimension One Spas section), PDF p.33 (printed p.29); spec table PDF p.7 (printed p.3)). Filbur Catalog & Reference Guide on 4CH-50 (Product by Pool/Spa Manufacturer (OEM), Dimension One Spas, printed p.33 (PDF p.17)). Hot Tub Outpost (retailer OEM listing) on 4CH-50 (01561-05: 4-3/4" x 14-3/4", handle, 1-1/2" MPT fine thread; 1991 Legend/Californian/Ambassador/Chancellor, 1992 Californian/Challenger/Legend 1500 Series, 1993 Arena; replaces Unicel 4CH-50, Filbur FC-0151).

Hot tubs listed for this cartridge

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

Model / systemYearsListed by
Dimension One Legend, Californian, Ambassador, Chancellor1991Hot Tub Outpost OEM listing
Dimension One Californian, Challenger, Legend 1500 Series1992Hot Tub Outpost OEM listing
Dimension One Arena1993Hot Tub Outpost OEM listing

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.

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All 12 Dimension One Spas spa filters

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