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.
PWK25-4 spa filter equivalents
Part number PWK25-4 appears in 1 cross-reference row below. Each row lists the OEM, Unicel and Pleatco numbers that the source documents treat as interchangeable, plus the cartridge size so you can confirm against your old filter.
The same numbers, on one page, are in the cross-reference lookup. A schedule for this part number, and the buy link, are on the replacement schedule and reorder page. Published intervals by brand are in the replace and clean calculator.
Hot Spring C-6600 cartridge (OEM 31115), 6-3/8" (162 mm) × 11-7/8" (302 mm), 45 sq ft. Unicel C-6600, Pleatco PWK25-4/PWK40.
Unicel C-6600
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| OEM | 31115 |
|---|---|
| Unicel | C-6600 |
| Pleatco | PWK25-4/PWK40 |
| Filbur | FC-3930 |
| Size | 6-3/8" (162 mm) × 11-7/8" (302 mm), 45 sq ft |
Sources
- Unicel 2026 Replacement Guide: OEM cross reference (Hot Spring section), PDF p.39 (printed p.35); spec table PDF p.13 (printed p.9) (PDF)
- Filbur Catalog & Reference Guide: Product by Pool/Spa Manufacturer (OEM), Hot Springs, printed p.38 (PDF p.20) (PDF)
Not in sources: no model/model-year fitment in sources.
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