PLAS35 / 5CH-203 / FC-0303
35 sq ft replacement filter cartridge • 5.375″ OD × 8.5625″ long
The PLAS35 shows up in LA Spas tubs and in American Whirlpool models numbered 250 through 282. It's a 35-square-foot cartridge with a handle on top and a 3-inch male-threaded base, so it screws down into the housing rather than dropping in. LA Spas numbers it HTF-303 and FD-51500, and the equivalents are Unicel 5CH-203 and Filbur FC-0303. The 3-inch threaded fitting is the detail that matters most. Plenty of same-diameter cartridges exist, but they won't thread into this housing. Check the base of your current filter, and if it screws in with a 3-inch thread, this is your match.
Compare on Amazon
PLAS35 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 | PLAS35 | Primary |
| Unicel | 5CH-203 | Equivalent |
| Filbur | FC-0303 | Equivalent |
| OEM | LA Spas HTF-303 | Original Equipment |
| OEM | LA Spas FD-51500 | Original Equipment |
Always verify dimensions and end-cap type before purchasing a replacement.
Compatible Hot Tubs & Spas
The PLAS35 (or any of its cross-references) fits these spa models. Cartridge sizing occasionally shifted between model years, so it's worth confirming against your owner's manual or the cartridge label.
| Brand | Model |
|---|---|
| LA Spas | Various |
| American Whirlpool | Models 250-282 |
Frequently Asked Questions
What are the dimensions of the PLAS35?
The PLAS35 is 5.375 inches in outer diameter, 8.5625 inches long, with a handle top and an open bottom. Total filtration area is 35 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 PLAS35?
PLAS35 is the same physical cartridge as 5CH-203, FC-0303, plus OEM versions like LA Spas HTF-303, LA Spas FD-51500. Same dimensions (5.375" × 8.5625"), same handle 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 LA Spas HTF-303 the same filter as the PLAS35?
Yes. LA Spas HTF-303 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 LA Spas HTF-303 (along with LA Spas FD-51500) and PLAS35, 5CH-203, FC-0303 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 PLAS35?
Mid-size spa cartridges like the PLAS35 (35 sq ft) usually last 12 to 24 months. It shows up most often in LA Spas tubs. The real driver is use: a tub that gets daily soaks for a couple of people burns through cartridges about twice as fast as one used a few times a month. A good rhythm is a monthly hose rinse, a deep soak in cleaner at every water change (every three to four months), and replacement once the pleats tear, the seams stain brown, or a soak no longer brings post-clean pressure back to baseline.
How do I clean the PLAS35?
The PLAS35 has a built-in handle on top, which means you can pull it without touching the media. 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 (or at every water change, whichever comes first), do a deep clean: overnight soak in a hot tub filter cleaner, then a thorough rinse. If your cartridge has a closed end cap, let it dry before reinstalling so you don't trap moisture inside the cartridge core.
Which hot tubs and spas use the PLAS35?
The PLAS35 is compatible with: LA Spas Various, American Whirlpool Models 250-282. Confirm against your owner's manual or the label inside the filter compartment, since some brands changed cartridge sizing between model years.
Dimensions
Specifications
| Outer Diameter | 5.375″ |
|---|---|
| Length | 8.5625″ |
| Top Type | Handle |
| Bottom Type | Open (no end cap) |
| Filtration Area | 35 sq ft |
| Primary Brand | Pleatco |
| Part Number | PLAS35 |
Fitment notes
Handle top, 3-inch MPT threaded bottom. LA Spas, American Whirlpool models 250/261/270/271/280/281/282.