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.
Dimension One Spas OEM 1561-04 spa filter (4CH-950)
Dimension One Spas (1-1/4" SAE thread)
Replacement numbers
Unicel 4CH-950, Pleatco PDO-UF25P2
Fits Dimension One Spas OEM 1561-04.
Diameter 4-5/8" (117 mm)Length 12" (305 mm)25 sq ft2 models listedUnicel 4CH-950
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| Unicel | 4CH-950 |
|---|---|
| Pleatco | PDO-UF25P2 (as printed in the Filbur catalog Dimension One Spas section (printed p.33); not found in the Pleatco 2023 Unicel cross reference) |
| Filbur | FC-0173 |
| Top | semi-circular handle |
| Bottom | 1-1/4" SAE thread |
Bottom: 1-1/4" SAE thread
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.
For Dimension One Spas, 4CH-950 cartridge (OEM 1561-04) sits in Dimension One Spas (1-1/4" SAE thread). The cross-reference prints OEM 1561-04; Unicel 4CH-950; Pleatco PDO-UF25P2; Filbur FC-0173. 4-5/8" across, 12" long, top semi-circular handle, bottom 1-1/4" SAE thread, 25 sq ft.
1561-04 carries this note from the catalogs: 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.
PDO-UF25P2 is the Pleatco string Filbur prints next to 4CH-950 (OEM 1561-04) on printed p.33. PDO-UF25P2 itself is absent from Pleatco’s 2023 Unicel cross-reference.
Model list attached to 4CH-950 cartridge (OEM 1561-04): Dimension One Little Dipper, years 1996–1998, listed by Hot Tub Outpost OEM listing; Dimension One El Nino, years 1991, listed by Hot Tub Outpost OEM listing.
Before ordering 4CH-950, compare it with 4CH-30 differs by Unicel 4CH-30, Pleatco PTL25P-4, Filbur FC-0141, 11-7/8" long, top molded cone handle, bottom 1-1/2” male thread/MPT, OEM 1561-14, note says Unicel's spec table rates 4CH-30 at 30 sq ft (4 oz media); its OEM cross reference and Filbur both give 25 sq ft for the Dimension One part, which is the figure shown.; and C-4340 differs by Unicel C-4340, Pleatco PMT40, Filbur FC-3081, 4-15/16" diameter, 11-5/8" long, top 2-1/8" / open, bottom 2-1/8" / open, 40 sq ft, OEM 1561-03, note says Discontinued by Dimension One Spas (noted in both the Unicel guide and the Filbur catalog); the replacement cartridge is still made..
Where those figures are printed: Unicel 2026 Replacement Guide on 4CH-950 (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-950 (Product by Pool/Spa Manufacturer (OEM), Dimension One Spas, printed p.33 (PDF p.17)). Hot Tub Outpost (retailer OEM listing) on 4CH-950 (01561-04: 4.62" x 11.50", handle, 1-1/4" SAE coarse thread; 1996–1998 Little Dipper, 1991 El Nino, also Saratoga Spas).
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 / system | Years | Listed by |
|---|---|---|
| Dimension One Little Dipper | 1996–1998 | Hot Tub Outpost OEM listing |
| Dimension One El Nino | 1991 | Hot 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.
The same 4CH-950 number is also on the Saratoga Spas page.
Other Dimension One Spas cartridges
- 4CH-30 cartridge (OEM 1561-14), 4-5/8" (117 mm) × 11-7/8" (302 mm)
- C-4340 cartridge (OEM 1561-03), 4-15/16" (125 mm) × 11-5/8" (295 mm)
- 4CH-50 cartridge (OEM 1561-05), 4-5/8" (117 mm) × 14-3/4" (375 mm)
- 4CH-940 cartridge (OEM 1561-13), 4-5/8" (117 mm) × 15" (381 mm)
- C-5404 cartridge (OEM 1561-09), 5-1/2" (140 mm) × 17" (432 mm)
- 7CH-552 cartridge (OEM 1561-10), 7" (178 mm) × 10-1/2" (267 mm)
All 12 Dimension One 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
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Leisure Time O Filter Clean Cartridge Cleaner Listing title: cartridge cleaner, 32 fl oz.
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SpaGuard Filter Cleaner Listing title: filter cleaner for spas and hot tubs, 1 quart.
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AquaChek SPA 6-in-1 Test Strips Listing title: reads total bromine, total chlorine, free chlorine, pH, total alkalinity and total hardness.
Unicel 4CH-950 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 (Dimension One Spas section), PDF p.33 (printed p.29); spec table PDF p.7 (printed p.3) (PDF)
- Filbur Catalog & Reference Guide: Product by Pool/Spa Manufacturer (OEM), Dimension One Spas, printed p.33 (PDF p.17) (PDF)
- Hot Tub Outpost (retailer OEM listing): 01561-04: 4.62" x 11.50", handle, 1-1/4" SAE coarse thread; 1996–1998 Little Dipper, 1991 El Nino, also Saratoga Spas (web page)