Watkins 1642301-1 Filter Cartridge
Watkins OEM number • 35 sq ft • 6.375″ OD × 14″ long
1642301-1 is Watkins's number for this cartridge, not a part you have to buy from Watkins. The filter itself is a 35 square foot cartridge measuring 6.375 inches across and 14 inches long, and Pleatco, Unicel, and Filbur all build it. If you read 1642301-1 off an old cartridge or found it in your manual, any of the numbers below drops into the same housing.
Watkins also lists 78161 and 78286 against this cartridge. Different numbers on paper, same filter in the box.
Fitment notes
For Hot Spring Limelight models from 2018 onward, and some Highlife NXT models from 2014. Watkins OEM numbers 78161 and 1642301-1 both refer to this cartridge. Unicel rates the equivalent C-6350 at 50 sq ft against Pleatco's 35; both describe the same 14-inch cartridge. Unicel also lists a C-6355 at 75 sq ft under the same OEM numbers, so check the square footage printed on your old cartridge before ordering.
What to buy instead
Replacements for the Watkins 1642301-1
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 | 1642301-1 | The number you searched |
| Pleatco | PWK35B | Aftermarket equivalent |
| Unicel | C-6350 | Aftermarket equivalent |
| Filbur | FC-3921 | Aftermarket equivalent |
| Watkins | 78161 | Other OEM number |
| Watkins | 78286 | Other OEM number |
Full specs, the cartridge diagram, and the complete compatibility list live on the PWK35B cartridge page. You can also see every 6.375″ × 14″ 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 1642301-1?
The PWK35B replaces it directly, and so does every cross-reference for it: C-6350, FC-3921. All of them are the same 35 sq ft cartridge at 6.375" outer diameter and 14" long. Buy whichever is cheapest at the time with solid recent reviews. The same cartridge also shows up as Watkins 78161, Watkins 78286, so those are not different filters either.
Is the Watkins 1642301-1 the same as the PWK35B?
Yes, physically the same filter. Watkins 1642301-1 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 1642301-1?
6.375 inches in outer diameter, 14 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.
Data updated August 2026