PBF35 / 8CH-950 / FC-0536
35 sq ft replacement filter cartridge • 8″ OD × 5.75″ long
This is the older Bullfrog cartridge, used on A-series and R-series tubs built before 2018. It's a short, wide 35-square-foot element, 8 inches across but under 6 inches tall, with open ends. Bullfrog part numbers include 10-2785, 10-1035, and 10-2870, and the cross-references are Unicel 8CH-950 and Filbur FC-0536. In 2018 Bullfrog moved to a coreless design (the PBF40), so the thing that matters most here is your tub's age. Pre-2018 tubs take this PBF35, later ones don't. If you're not certain, the printed part number on your current cartridge settles it instantly.
Compare on Amazon
PBF35 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 | PBF35 | Primary |
| Unicel | 8CH-950 | Equivalent |
| Filbur | FC-0536 | Equivalent |
| OEM | Bullfrog 10-2785 | Original Equipment |
| OEM | Bullfrog 10-1035 | Original Equipment |
| OEM | Bullfrog 10-2870 | Original Equipment |
Always verify dimensions and end-cap type before purchasing a replacement.
Compatible Hot Tubs & Spas
The PBF35 (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 PBF35?
The PBF35 is 8 inches in outer diameter, 5.75 inches long, with an open top and an open bottom. Total filtration area is 35 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 PBF35?
PBF35 is the same physical cartridge as 8CH-950, FC-0536, plus OEM versions like Bullfrog 10-2785, Bullfrog 10-1035, Bullfrog 10-2870. Same dimensions (8" × 5.75"), same open 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 Bullfrog 10-2785 the same filter as the PBF35?
Yes. Bullfrog 10-2785 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 Bullfrog 10-2785 (along with Bullfrog 10-1035, Bullfrog 10-2870) and PBF35, 8CH-950, FC-0536 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 PBF35?
Mid-size spa cartridges like the PBF35 (35 sq ft) usually last 12 to 24 months. It shows up most often in Bullfrog tubs. The real driver is use: a tub that gets daily soaks for a couple of people burns through cartridges about twice as fast as one used a few times a month. A good rhythm is a monthly hose rinse, a deep soak in cleaner at every water change (every three to four months), and replacement once the pleats tear, the seams stain brown, or a soak no longer brings post-clean pressure back to baseline.
How do I clean the PBF35?
The PBF35 has open ends on both top and bottom, so water flows straight through. 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 PBF35?
The PBF35 is compatible with: Bullfrog A-Series, Bullfrog R-Series. 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 | 5.75″ |
| Top Type | Open (no end cap) |
| Bottom Type | Open (no end cap) |
| Filtration Area | 35 sq ft |
| Primary Brand | Pleatco |
| Part Number | PBF35 |
Fitment notes
Bullfrog A-series and R-series older models (pre-2018).