PCD100W / C-8399 / FC-3965
100 sq ft replacement filter cartridge • 8″ OD × 16.5″ long
This is the largest of the Caldera cartridges, a 100-square-foot element with a molded handle on top and a wide 3-5/8-inch open base. It's the filter for the newer Utopia Series tubs (Geneva, Niagara, Tahitian, Elation, and the rest) from 2005 onward. Caldera part numbers include 73722, 1039607, and 81004, and the cross-references are Unicel C-8399 and Filbur FC-3965. The handle makes this one easy to service. Grab it and lift straight up. Just don't mix it up with the smaller Paradise-series cartridges. At 8 inches across and 16-1/2 inches tall it's noticeably bigger, and only the Utopia housings are built to take it.
Compare on Amazon
PCD100W replacements on Amazon
The buttons below pull up Amazon results for each cross-reference part number. Same physical cartridge, different stickers, often different prices. Cross-shop and pick the cheapest option that has solid recent reviews.
Cross-Reference & Interchangeable Part Numbers
| Brand | Part Number | Type |
|---|---|---|
| Pleatco | PCD100W | Primary |
| Unicel | C-8399 | Equivalent |
| Filbur | FC-3965 | Equivalent |
| OEM | Caldera 73722 | Original Equipment |
| OEM | Caldera 1039607 | Original Equipment |
| OEM | Caldera 81004 | Original Equipment |
Always verify dimensions and end-cap type before purchasing a replacement.
Compatible Hot Tubs & Spas
The PCD100W (or any of its cross-references) fits these spa models. Cartridge sizing occasionally shifted between model years, so it's worth confirming against your owner's manual or the cartridge label.
Frequently Asked Questions
What are the dimensions of the PCD100W?
The PCD100W is 8 inches in outer diameter, 16.5 inches long, with a handle top and an open bottom. Total filtration area is 100 square feet. Before ordering, pull your existing cartridge and measure it yourself, or check the label inside the housing. OD and length both have to match within about an eighth of an inch, and the end-cap style needs to match exactly so the cartridge seats properly when the lid closes.
What other part numbers are interchangeable with the PCD100W?
PCD100W is the same physical cartridge as C-8399, FC-3965, plus OEM versions like Caldera 73722, Caldera 1039607, Caldera 81004. Same dimensions (8" × 16.5"), same handle top, same open bottom. The Pleatco, Unicel, and Filbur boxes ship the same media inside, just with different stickers. The only thing to watch is the end-cap style: if a cross-reference has a slightly different cap design, it may not seat right in your housing.
Is the Caldera 73722 the same filter as the PCD100W?
Yes. Caldera 73722 is an OEM number, the code the tub or pool builder stamps on the cartridge they ship. The filter itself is made by Pleatco, Unicel, or Filbur, so Caldera 73722 (along with Caldera 1039607, Caldera 81004) and PCD100W, C-8399, FC-3965 all point to one interchangeable cartridge. Buy whichever is cheapest with solid recent reviews, and just check that the dimensions match your old cartridge before you order.
How often should I replace the PCD100W?
100 sq ft is a lot of media for a hot tub, so the PCD100W tends to outlast the small-format spa cartridges. It shows up most often in Caldera tubs. Two adults soaking a couple times a week can usually get 18 to 24 months out of one. Monthly hose rinses and a quarterly overnight soak stretch that further. Replace it when the pleats won't rinse clean or pressure starts climbing in a way soaking can't fix.
How do I clean the PCD100W?
The PCD100W has a built-in handle on top, which means you can pull it without touching the media. Pull the cartridge from the housing and hose it down. Hit the pleats from above at about a 45-degree angle so water rinses debris out instead of packing it deeper, and work top to bottom while rotating the cartridge. Skip the pressure washer. The high pressure tears or collapses pleats, and once that happens you've lost media that doesn't come back. Every few months (or at every water change, whichever comes first), do a deep clean: overnight soak in a hot tub filter cleaner, then a thorough rinse. If your cartridge has a closed end cap, let it dry before reinstalling so you don't trap moisture inside the cartridge core.
Which hot tubs and spas use the PCD100W?
The PCD100W is compatible with: Caldera Geneva, Caldera Niagara, Caldera Utopia, Caldera Vacanza, Caldera Salina, Caldera Marino. Confirm against your owner's manual or the label inside the filter compartment, since some brands changed cartridge sizing between model years.
Dimensions
Specifications
| Outer Diameter | 8″ |
|---|---|
| Length | 16.5″ |
| Top Type | Handle |
| Bottom Type | Open (no end cap) |
| Filtration Area | 100 sq ft |
| Primary Brand | Pleatco |
| Part Number | PCD100W |
Fitment notes
Handle top, 3-5/8 inch open base. Caldera Utopia Series 2005+: Niagara, Geneva, Tahitian, Elation, Aspire, Cantabria (2014+ Q3+).