PRB25-IN / C-4326 / FC-2375 / Beachcomber 3005845 / Pentair 17-2327 / Pentair R173429
25 sq ft replacement filter cartridge • 5″ OD × 13.9375″ long
If you own a Beachcomber, this is almost certainly your cartridge. The PRB25-IN has been the standard drop-in for Beachcomber tubs built since 1994. It's easy to spot: open ends with 2-1/8-inch holes top and bottom, and it sits straight down into the filter well with no threads to line up. Beachcomber sells the same part as 3005845, and both Unicel (C-4326) and Filbur (FC-2375) make identical replacements. One catch. At 25 square feet it's on the small side, so it works hard and wears out faster than a bigger element. Rinse it every couple of weeks, and plan to replace it more often than you would a 50-plus cartridge.
Compare on Amazon
PRB25-IN 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 | PRB25-IN | Primary |
| Unicel | C-4326 | Equivalent |
| Filbur | FC-2375 | Equivalent |
| OEM | Beachcomber 3005845 | Original Equipment |
| OEM | Pentair 17-2327 | Original Equipment |
| OEM | Pentair R173429 | Original Equipment |
| OEM | Waterway 817-2500 | Original Equipment |
| OEM | Hot Spring 33521 | Original Equipment |
| OEM | Coleman/Maax 100586 | Original Equipment |
| OEM | Coleman/Maax 3301-2242 | Original Equipment |
| OEM | Custom Molded Products 25392 | Original Equipment |
Always verify dimensions and end-cap type before purchasing a replacement.
Compatible Hot Tubs & Spas
The PRB25-IN (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.
| Brand | Model |
|---|---|
| Beachcomber | All models 1994+ |
Frequently Asked Questions
What are the dimensions of the PRB25-IN?
The PRB25-IN is 5 inches in outer diameter, 13.9375 inches long, with an open top and an open bottom. Total filtration area is 25 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 PRB25-IN?
PRB25-IN is the same physical cartridge as C-4326, FC-2375, plus OEM versions like Beachcomber 3005845, Pentair 17-2327, Pentair R173429, Waterway 817-2500, Hot Spring 33521, Coleman/Maax 100586, Coleman/Maax 3301-2242, Custom Molded Products 25392. Same dimensions (5" × 13.9375"), 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 Beachcomber 3005845 the same filter as the PRB25-IN?
Yes. Beachcomber 3005845 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 Beachcomber 3005845 (along with Pentair 17-2327, Pentair R173429, Waterway 817-2500, Hot Spring 33521, Coleman/Maax 100586, Coleman/Maax 3301-2242, Custom Molded Products 25392) and PRB25-IN, C-4326, FC-2375 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 PRB25-IN?
25 sq ft is small. It shows up most often in Beachcomber tubs. The PRB25-IN has to filter the same hot tub water as a 50 sq ft cartridge, just twice as fast, so it wears faster too. Plan on 12 to 18 months in a normally used tub, closer to a year if the spa gets daily soaks or a crowd. Rinse it monthly between water changes and soak it in filter cleaner each quarter. When a soak stops dropping the post-rinse pressure, replace it.
How do I clean the PRB25-IN?
The PRB25-IN 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 PRB25-IN?
The PRB25-IN is compatible with: Beachcomber All models 1994+. 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 | 5″ |
|---|---|
| Length | 13.9375″ |
| Top Type | Open (no end cap) |
| Bottom Type | Open (no end cap) |
| Filtration Area | 25 sq ft |
| Primary Brand | Pleatco |
| Part Number | PRB25-IN |
Fitment notes
2-1/8 inch top and bottom opening. Drop-in style. Used in Beachcomber 1994-present. Also the replacement for Pentair Rainbow Dynamic 25 in-line filters (Dynamic Series I RDC-25 through Series IV DFM/DFML), Hot Spring and Hot Spot skim filters (33521), Coleman Spas, and Waterway 25 sq ft top-load housings. For more capacity in the same housing see PRB37-IN or PRB50-IN.