Pentair 17-2021 Filter Cartridge
Pentair OEM number • 13 sq ft • 2.6875″ OD × 19.6875″ long
17-2021 is Pentair's number for this cartridge, not a part you have to buy from Pentair. The filter itself is a 13 square foot cartridge measuring 2.6875 inches across and 19.6875 inches long, and Pleatco, Unicel, and Filbur all build it. If you read 17-2021 off an old cartridge or found it in your manual, any of the numbers below drops into the same housing.
Pentair also lists 17-2047 and R173326 against this cartridge. Different numbers on paper, same filter in the box.
Fitment notes
1-1/16 inch open top and bottom. Replacement for the Pentair Rainbow Lifeguard CL-19X and Rainbow MX-series module filters; also used in the Jacuzzi Whirlpool Bath Cambio, where Pleatco sells the identical cartridge as the PJW12. Both manufacturer sheets rate it 13 sq ft despite the 12 in the name. Unicel has discontinued the C-2612 equivalent.
What to buy instead
Replacements for the Pentair 17-2021
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 |
|---|---|---|
| Pentair | 17-2021 | The number you searched |
| Pleatco | PRB12 | Aftermarket equivalent |
| Unicel | C-2612 | Aftermarket equivalent |
| Filbur | FC-2340 | Aftermarket equivalent |
| Jacuzzi | 2945000 | Other OEM number |
| Pentair | 17-2047 | Other OEM number |
| Pentair | R173326 | Other OEM number |
Full specs, the cartridge diagram, and the complete compatibility list live on the PRB12 cartridge page. You can also see every 2.6875″ × 19.6875″ cartridge if you are checking a measurement rather than a part number.
Frequently Asked Questions
What filter replaces the Pentair 17-2021?
The PRB12 replaces it directly, and so does every cross-reference for it: C-2612, FC-2340. All of them are the same 13 sq ft cartridge at 2.6875" outer diameter and 19.6875" long. Buy whichever is cheapest at the time with solid recent reviews. The same cartridge also shows up as Jacuzzi 2945000, Pentair 17-2047, Pentair R173326, so those are not different filters either.
Is the Pentair 17-2021 the same as the PRB12?
Yes, physically the same filter. Pentair 17-2021 is an OEM number, meaning it is the code Pentair put on the cartridge that shipped with the equipment. Pentair 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 Pentair 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 Pentair 17-2021?
2.6875 inches in outer diameter, 19.6875 inches long, with 13 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