4-15/16" × 14-7/8"
Nordic Hot Tubs spa filters
Nordic Hot Tubs publishes its own filter chart. Most Nordic spas take the 25 sq ft CARTRIDGE (Unicel C-4326); several models built after September 2021 take the 45 sq ft CARTRIDGE-E, and the Crown (after 2014), D’Amour, Encore, Jubilee, Retreat and Stella take the threaded 35 sq ft CARTRIDGE-T35 (Unicel 4CH-935). The Unicel and Filbur catalogs also list a C-4301 for Nordic models dated before 7/99, which Nordic’s chart does not mention.
The full model list, the Bella cartridges and the places where Nordic’s chart, manual and the catalogs disagree are on the Nordic filter-by-model page. Rows that duplicate a cartridge already covered under another brand are kept out of search results; confirm your size before ordering.
This page lists 3 Nordic Hot Tubs replacement cartridges from the Unicel 2026 Replacement Guide, the Pleatco 2023 catalog, the Filbur catalog and manufacturer and retailer pages, plus model and model-year fitment for 2 of them (12 hot tub models in total). 2 have 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.
- C-4301C-4301, 4-15/16" (125 mm) × 14-7/8" (378 mm)See replacement
- 31CARTRIDGEC-4326, 4-15/16" (125 mm) × 13-5/16" (338 mm)See replacement
- CARTRIDGE-T35; 31CARTRIDGE-T354CH-935, 4-15/16" (125 mm) × 9-1/4" (235 mm)See replacement
| Cartridge | Unicel | Pleatco | Filbur | Size | Fits | Status |
|---|---|---|---|---|---|---|
| C-4301 (Nordic Hot Tubs (models dated before 7/99)) | C-4301 | PMT27.5 | FC-1610 | 4-15/16" (125 mm) × 14-7/8" (378 mm), 28 sq ft | not listed | verified |
| 31CARTRIDGE | C-4326 | PRB25-IN | FC-2375 | 4-15/16" (125 mm) × 13-5/16" (338 mm), 25 sq ft | 6 models | verified |
| CARTRIDGE-T35; 31CARTRIDGE-T35 | 4CH-935 | PWW35L | not listed | 4-15/16" (125 mm) × 9-1/4" (235 mm), 35 sq ft | 7 models | verified |
Know your model but not the part number? See Nordic Hot Tubs filter by model and year.
2 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 Nordic Hot Tubs
- Waterway Plastics, same part numbers C-4326, 4CH-935
- Beachcomber, same part number C-4326
- Coleman Spas, same part number C-4326
- Hot Spot, same part number C-4326
- Hot Spring, same part number C-4326
Guides that apply to Nordic Hot Tubs
- Open-end vs threaded hot tub filters
- How Filbur, Unicel and Pleatco numbers compare
- How to find your spa filter size
- How to install a cartridge
- All guides
Search Nordic Hot Tubs 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
-
C-4301 cartridge -
C-4326 cartridge 4-15/16" × 13-5/16"
-
4CH-935 cartridge 4-15/16" × 9-1/4"
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.