PSR70-4 / UHD-SR70 / FC-2540
70 sq ft replacement filter cartridge • 8.6875″ OD × 18.1875″ long
Sta-Rite's Posi-Flo 70TX takes this 70-square-foot cartridge. It's easy to get wrong, because it's physically the same size as the 50-square-foot PSR50: same 8-11/16-inch diameter, same 18-inch height. The difference is media density. The 70TX packs more pleated surface area into the identical can, so you can't tell them apart by measuring. You have to go by the tank model or the number on the old cartridge. Sta-Rite numbers include PTM70, 70TXR, and 70TX, and the cross-references are Unicel UHD-SR70 and Filbur FC-2540. If your Posi-Flo tank is a 70, this is your cartridge, and it's worth getting right, since the 70 gives you more filtration and longer runs between cleanings than the 50.
Compare on Amazon
PSR70-4 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 | PSR70-4 | Primary |
| Unicel | UHD-SR70 | Equivalent |
| Filbur | FC-2540 | Equivalent |
| OEM | Sta-Rite PTM70 | Original Equipment |
| OEM | Sta-Rite 70TXR | Original Equipment |
| OEM | Sta-Rite 70TX | Original Equipment |
Always verify dimensions and end-cap type before purchasing a replacement.
Compatible Pool Filter Systems
| Brand | Model |
|---|---|
| Sta-Rite | Posi-Flo 70TX |
Frequently Asked Questions
What are the dimensions of the PSR70-4?
The PSR70-4 is 8.6875 inches in outer diameter, 18.1875 inches long, with an open top and an open bottom. Total filtration area is 70 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 PSR70-4?
PSR70-4 is the same physical cartridge as UHD-SR70, FC-2540, plus OEM versions like Sta-Rite PTM70, Sta-Rite 70TXR, Sta-Rite 70TX. Same dimensions (8.6875" × 18.1875"), 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 Sta-Rite PTM70 the same filter as the PSR70-4?
Yes. Sta-Rite PTM70 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 Sta-Rite PTM70 (along with Sta-Rite 70TXR, Sta-Rite 70TX) and PSR70-4, UHD-SR70, FC-2540 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 PSR70-4?
At 70 sq ft the PSR70-4 runs smaller than the big 100-plus sq ft pool cartridges, so it has less buffer between cleanings. Expect 12 to 18 months in normal use, less if the pool sees heavy traffic or the chemistry drifts. Watch the gauge: when pressure sits 8 to 10 psi above the clean starting point and a soak won't drop it, put in a fresh one.
How do I clean the PSR70-4?
The PSR70-4 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, give it a deeper clean: soak in a dedicated pool filter cleaner per the product's dwell time, then rinse it down completely before reinstalling. Keeping a spare cartridge on the shelf is genuinely worth it. You swap, run the soak overnight, and the pool keeps filtering.
Which hot tubs and spas use the PSR70-4?
Pull your existing cartridge and read the part number off the end cap, or check the label inside the filter compartment. That's the most reliable way to confirm compatibility.
Dimensions
Specifications
| Outer Diameter | 8.6875″ |
|---|---|
| Length | 18.1875″ |
| Top Type | Open (no end cap) |
| Bottom Type | Open (no end cap) |
| Filtration Area | 70 sq ft |
| Primary Brand | Pleatco |
| Part Number | PSR70-4 |
Fitment notes
Sta-Rite Posi-Flo 70TX / Swim-Thru series.