6" × 5-1/2"
Softub spa filters
Most Softub spas use a snap-on spa filter that pushes over the suction cover rather than a threaded cartridge: Softub dealers sell the 5020 (P/N 2003905) for tubs built from mid-2009 and the 5015 or 5010 for older tubs. Those snap-on filters are not in the Unicel, Pleatco or Filbur catalogs.
The catalogs do list two threaded cartridges for Softub: the 6" × 5-1/2" 6CH-25 under OEM 90-802 (Pleatco names the matching PTL20W-SV-P4 for both Softub and Leisure Bay, and rates it at 20 sq ft against Unicel’s 25) and a smaller 4-5/8" × 6-3/4" 4CH-20 with no OEM number, which stays flagged for verification.
This page lists 2 Softub replacement cartridges from the Unicel 2026 Replacement Guide, the Pleatco 2023 catalog and the Filbur catalog, plus model and model-year fitment for 1 of them (1 hot tub models in total). 1 has a Filbur number. Find your spa filter by the OEM part number on the end cap, or measure it and compare sizes below.
Clean and replace intervals for one cartridge on this list, plus the cross-reference numbers and a buy link: filter replacement schedule and reorder.
- 90-8026CH-25, 6" (152 mm) × 5-1/2" (140 mm)See replacement
- 4CH-204CH-20, 4-5/8" (117 mm) × 6-3/4" (171 mm)See replacement
| Cartridge | Unicel | Pleatco | Filbur | Size | Fits | Status |
|---|---|---|---|---|---|---|
| 90-802 | 6CH-25 | PTL20W-SV-P4 | FC-0305 | 6" (152 mm) × 5-1/2" (140 mm), 25 sq ft | 1 model | verified |
| 4CH-20 (Softub) | 4CH-20 | not listed | not listed | 4-5/8" (117 mm) × 6-3/4" (171 mm), 20 sq ft | not listed | unverified |
Know your model but not the part number? See Softub filter by model and year.
1 of these rows do not have enough detail for a stand-alone page (for example, no OEM number or no second cross-reference), so their pages are kept out of search results and this table is the main reference for them.
Brands that share cartridges with Softub
- Master Spas, same part number 4CH-20
- Saratoga Spas, same part number 4CH-20
Guides that apply to Softub
- How Filbur, Unicel and Pleatco numbers compare
- Open-end vs threaded hot tub filters
- How to find your spa filter size
- How to install a cartridge
- All guides
Search Softub part numbers on Amazon
Each button opens an Amazon search for that part number. The cartridge page is where the cited size and fittings are. Match those before you buy.
Part numbers from this table
-
6CH-25 cartridge (OEM 90-802) -
4CH-20 cartridge 4-5/8" × 6-3/4"
Disclosure: we may earn a commission from qualifying purchases made through retailer links on this site, at no extra cost to you. As an Amazon Associate I earn from qualifying purchases. Amazon links on this page go to Amazon.com and are affiliate links; they never change what we write, and the list is not ranked by commission. Each “Search on Amazon” button opens an Amazon search for the part or product name shown, not a single listing we pre-checked. Check size, quantity and your spa maker’s guidance before you buy. See our affiliate disclosure.
Model-year fitment comes only from the sources named on each cartridge page. Where no source lists models or years, the page says so.