Home › Caldera › C-8399 cartridge (OEM 1039607)
Caldera OEM 1039607 spa filter (C-8399)
Listed for: Caldera (Watkins)
Fits Caldera OEM 1039607, 73722 cited
Ø 8"L 16-1/2"100 sq ft| Unicel | C-8399 |
|---|---|
| Pleatco | PCD100W |
| Filbur | not sourced |
| Top | semi-circular handle |
| Bottom | 3-5/8" / open w/ lip seal |
Retailer search links — see disclosure. Verify dimensions before ordering.
How to confirm this is your filter
Pull your current cartridge and measure it end to end, including any handle, and across the widest point of the pleats. This cartridge measures 8" in diameter and 16-1/2" long, with a semi-circular handle on top and a 3-5/8" / open w/ lip seal on the bottom. The bottom fitting matters most: a cartridge with the right diameter but the wrong thread or open-end size will not seal in the filter housing, letting unfiltered water bypass the media.
The 100 sq ft rating describes the pleated media area. Caldera housings are designed around a particular cartridge, so choose a replacement with the same size and fittings rather than a larger area rating. Unicel C-8399 and Pleatco PCD100W are cross-referenced to each other in the Pleatco 2023 catalog, so either should fit the same housing. Caldera has used 2 OEM numbers for this cartridge; any of them should map to the same replacement.
Similar-diameter Caldera cartridges
- C-8300 cartridge (OEM 74817) — 8" × 16-1/2"
Sources
- Unicel 2026 Replacement Guide — OEM Cross Reference, PDF p.29; spec table PDF p.19 (PDF)
- Pleatco 2023 Catalog — Unicel-to-Pleatco cross reference, PDF p.43 (PDF)
Not in sources: no Filbur equivalent sourced; no model-year range in source.