Watkins 31114 Filter Cartridge
Watkins OEM number • 65 sq ft • 8.5″ OD × 10.5″ long
31114 is Watkins's number for this cartridge, not a part you have to buy from Watkins. The filter itself is a 65 square foot cartridge measuring 8.5 inches across and 10.5 inches long, and Pleatco, Unicel, and Filbur all build it. If you read 31114 off an old cartridge or found it in your manual, any of the numbers below drops into the same housing.
Watkins also lists 71827 and 71828 against this cartridge. Different numbers on paper, same filter in the box.
Fitment notes
3-inch top and bottom openings. Also fits the Hot Spring Highlife Classic, 1989 and 1990. Limelight models built from 2008 to 2017 use this cartridge, and the 2018 and later Limelight tubs switched to the PWK35B, so check your build year before ordering. Pleatco lists this as the upgrade from the PWK45N, and Unicel consolidates both into the C-8465.
What to buy instead
Replacements for the Watkins 31114
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 |
|---|---|---|
| Watkins | 31114 | The number you searched |
| Pleatco | PWK65 | Aftermarket equivalent |
| Unicel | C-8465 | Aftermarket equivalent |
| Filbur | FC-3960 | Aftermarket equivalent |
| Caldera | 76136 | Other OEM number |
| Watkins | 71827 | Other OEM number |
| Watkins | 71828 | Other OEM number |
Full specs, the cartridge diagram, and the complete compatibility list live on the PWK65 cartridge page. You can also see every 8.5″ × 10.5″ cartridge if you are checking a measurement rather than a part number.
Equipment that uses this cartridge
Looking for a different model? Browse every Watkins model we cover.
Frequently Asked Questions
What filter replaces the Watkins 31114?
The PWK65 replaces it directly, and so does every cross-reference for it: C-8465, FC-3960. All of them are the same 65 sq ft cartridge at 8.5" outer diameter and 10.5" long. Buy whichever is cheapest at the time with solid recent reviews. The same cartridge also shows up as Caldera 76136, Watkins 71827, Watkins 71828, so those are not different filters either.
Is the Watkins 31114 the same as the PWK65?
Yes, physically the same filter. Watkins 31114 is an OEM number, meaning it is the code Watkins put on the cartridge that shipped with the equipment. Watkins 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 Watkins 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 Watkins 31114?
8.5 inches in outer diameter, 10.5 inches long, with 65 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