Waterway 817-3510 Filter Cartridge
Waterway OEM number • 35 sq ft • 5″ OD × 4.625″ long
817-3510 is Waterway's number for this cartridge, not a part you have to buy from Waterway. The filter itself is a 35 square foot cartridge measuring 5 inches across and 4.625 inches long, and Pleatco, Unicel, and Filbur all build it. If you read 817-3510 off an old cartridge or found it in your manual, any of the numbers below drops into the same housing.
Fitment notes
2-1/8 inch open top and bottom. Sold and used as a set of two short cartridges, 35 sq ft per pair. Fits Pentair Rainbow Dynamic Series IV Model DSF-35 skim filters and Beachcomber 3005820. Sundance (6000-134) pairs one of these with the 25 sq ft skim cartridge for 45 sq ft total.
What to buy instead
Replacements for the Waterway 817-3510
Each button searches Amazon for one of the numbers this cartridge is sold under. The OEM version is usually the most expensive of the set and the aftermarket versions are the same physical filter, so it is worth checking all of them before you order.
Every number for this filter
| Brand | Part Number | Type |
|---|---|---|
| Waterway | 817-3510 | The number you searched |
| Pleatco | PRB17.5SF-PAIR | Aftermarket equivalent |
| Unicel | C-4401 | Aftermarket equivalent |
| Filbur | FC-2386 | Aftermarket equivalent |
| Beachcomber | 3005820 | Other OEM number |
| Pentair | 17-2606 | Other OEM number |
| Pentair | R173432 | Other OEM number |
| Sundance | 6000-134 | Other OEM number |
Full specs, the cartridge diagram, and the complete compatibility list live on the PRB17.5SF-PAIR cartridge page. You can also see every 5″ × 4.625″ cartridge if you are checking a measurement rather than a part number.
Frequently Asked Questions
What filter replaces the Waterway 817-3510?
The PRB17.5SF-PAIR replaces it directly, and so does every cross-reference for it: C-4401, FC-2386. All of them are the same 35 sq ft cartridge at 5" outer diameter and 4.625" long. Buy whichever is cheapest at the time with solid recent reviews. The same cartridge also shows up as Beachcomber 3005820, Pentair 17-2606, Pentair R173432, Sundance 6000-134, so those are not different filters either.
Is the Waterway 817-3510 the same as the PRB17.5SF-PAIR?
Yes, physically the same filter. Waterway 817-3510 is an OEM number, meaning it is the code Waterway put on the cartridge that shipped with the equipment. Waterway does not manufacture cartridges. Pleatco, Unicel, and Filbur do, and they sell the identical part under their own numbers at a lower price. Match the dimensions against your old cartridge before ordering and you are covered.
Do I have to buy the Waterway version?
No. Nothing about the housing requires an OEM-branded cartridge, and the warranty on your equipment is not voided by using an aftermarket filter that meets the same spec. The reason to buy OEM is convenience, not performance. The reason not to is price, which is often a meaningful gap for an identical part. What matters is that outer diameter, length, and end-cap style all match.
What size is the Waterway 817-3510?
5 inches in outer diameter, 4.625 inches long, with 35 square feet of filter media. Both measurements need to land within about an eighth of an inch, and the end caps have to match so the cartridge seats correctly when you close the lid. Measure your old one rather than trusting a number that has worn off the label.
Last verified August 2026