A cloudy hot tub or a green-tinted pool is rarely about the water you pour in. It is almost always about the cartridge doing the filtering, and most homeowners only notice it when the system starts gasping or the water turns hazy. The right pool and spa filters keep debris, oils, and fine particles in check, and the wrong size or material sends your sanitizer chasing problems it cannot win.
This roundup walks through eight replacement cartridges built for common above-ground pools, inflatable spas, and built-in hot tubs. Each entry is mapped to the system it actually fits, with honest trade-offs and a clear picture of who gets the most from it. Browse with your current model number in hand and you will land on a match within a few minutes.
A Fast Comparison Of The Options
Intex 29011E Type S1 PureSpa Replacement Cartridges (6 Filters)
POOLPURE 5CH-35 Spa Filter Replacement
POOLPURE C-8465 Spa Filter for Watkins 31114 (2 Pack)
Unicel C-8411 Replacement Cartridge for 75 sq ft Filters
POOLPURE 5CH-352 Spa Filter (2 Pack) for Marquis Models
POOLPURE PRB50-IN Antimicrobial Hot Tub Filter (2 Pack)
POOLPURE PRB25-IN Hot Tub Filter (2 Pack)
POOLPURE 5CH-352 Spa Filter for Marquis Spa Models
Why These Options Stand Out
If you run an Intex PureSpa on the patio, this is the cartridge that came in the box, so fitting is rarely a question. The S1 spec is built around Dacron paper media, which catches fine particles while still letting the pump move water at its normal rate. For anyone who treats their hot tub like a weekly routine rather than a weekend project, that familiar feel matters.
The six-pack format solves a real annoyance. Cartridges in this category need rinsing weekly and a full swap every month or so during heavy use, so a single replacement leaves you scrambling in a few weeks. For PureSpa owners, depending on how often the tub sees use, this bundle can carry a full season without a reorder, depending on bather load and water chemistry.
A Strong Showing
- Direct OEM fit for Intex PureSpa systems, no guesswork on dimensions
- Heavy-duty Dacron media holds up to repeated rinsing without tearing
- Multi-pack covers roughly six months of typical maintenance cycles
- Cleaning takes a garden hose and a few minutes, no specialty tools
Worth Noting
- Built specifically for PureSpa, so it does not cross over to standard pool systems
- Sediment-heavy environments may shorten the working life of each cartridge
- Not compatible with Type S2 PureSpa setups, so check your model before ordering
Quick Facts
Right Fit For
Intex PureSpa owners who want a single seasonal order instead of monthly reorders.
Consider Something Else When
You run a non-Intex spa, in which case the POOLPURE 5CH-35 is a more flexible option for the same kind of compact housing.
Smaller inflatable spas need cartridges that fit snug inside a tight housing, and the 5CH-35 spec from POOLPURE is built for that exact job. With an 8-inch length and a 5 3/4-inch outside diameter, it slides into the same slot as Unicel 5CH-35 and Filbur FC-0300, which makes cross-shopping straightforward. The top handle is a small touch that earns its place during weekly rinses.
For first-time hot tub owners who have inherited a system without paperwork, the cross-reference list printed on the listing does the heavy lifting. You match your current cartridge to one of the named equivalents, then order with confidence. Compared to the Intex S1 above, this one targets mainstream spas rather than a single brand.
Why It Works Well
- Covers Unicel, Filbur, and several OEM part numbers in one cartridge
- Compact 8-inch body fits tight skimmer openings
- Trilobal fabric media balances flow and fine-particle capture
- Top handle simplifies removal when the housing is full of water
Trade Offs
- Single cartridge order means more frequent reorders than a multi-pack
- Not sized for full-size pools, so it stays in spa territory
Made For
Hot tub owners running compact spas that use a 5CH-35, FC-0300, or PMAX50P4 spec cartridge.
Look Elsewhere When
You need a multi-pack, in which case the POOLPURE 5CH-352 (Item 5) is a better match for Marquis models with similar dimensions.
Step up to a larger hot tub and the cartridge needs to grow with it. The C-8465 brings 65 square feet of filtration surface to the job, a meaningful jump from the 35 sq ft you find on the more compact 5CH series. For Watkins, Hot Spring, and Tiger River spas, that media area translates to longer intervals between rinses and a more forgiving maintenance routine.
The two-pack format also fits the way owners of bigger tubs actually shop. Replacing one cartridge at a time leads to downtime, so having the spare on the shelf means you can swap and keep the water moving the same day. Compared to the 5CH-35 above, this is the workhorse version of the same idea.
Practical Pluses
- 65 sq ft media area extends time between cleanings under normal use
- Compatible with Watkins 31114, Unicel C-8465, and Filbur FC-3960
- Trilobal fabric handles oils from bathers more effectively than basic paper
- Two-pack rotation reduces the temptation to over-extend a worn cartridge
Honest Caveats
- Larger body will not fit 5CH-style housings, so sizing is critical
- Heavier than compact cartridges, and a wet one is awkward to lift one-handed
Best Suited To
Owners of full-size Watkins, Hot Spring Tempo, and Tiger River spas with a 31114 or C-8465 spec.
Reach For A Different Pick When
You run a smaller Hot Spring or Limelight spa, in which case the Unicel C-8411 (Item 4) is built for those systems.
Unicel sits in the OEM lane, and the C-8411 carries that reputation into larger pool and spa systems. The 8 15/16-inch diameter and 17 3/8-inch length match a wide range of Hayward, Sta-Rite, and Waterway setups, which is why this cartridge has been a go-to for service techs for years. Open-end gaskets on both caps give the seal a tight, predictable feel during install.
Pool owners running a 75 sq ft system will notice the difference in two places: the cartridge slides in without forcing, and the end caps sit flat against the housing. For someone managing a dedicated equipment pad rather than a small backyard spa, that kind of predictable fit reduces the chance of a bypass leak that lets debris circle back into the water.
Advantages To Know
- Direct cross for Hayward CX760RE, Sta-Rite PXC-75, and Waterway Pro Clean 75
- Open end caps with molded gaskets create a clean seal at install
- OEM-tier build quality aimed at service-grade pools
- 75 sq ft media area supports longer run cycles on larger systems
Points To Note
- Single cartridge, so plan to keep a spare on hand for rotation
- Length and diameter will not fit compact spa housings from earlier picks
At A Glance
Whose Shelf It Belongs On
Pool owners with Hayward, Sta-Rite, or Waterway 75 sq ft cartridge systems who want OEM-grade fit.
Swap It Out When
You maintain a smaller spa instead, since the C-8465 (Item 3) covers the common Watkins sizes in a friendlier footprint.
Marquis hot tubs use a distinctive 2-inch male threaded base, and the 5CH-352 is built around exactly that connection. At 12 3/16 inches long with a 5 1/4-inch outside diameter, it lands in the middle of the spa-size scale, larger than the 5CH-35 but slimmer than the C-8465. The 2-pack format keeps a fresh cartridge ready the moment the first one tires out.
For owners of Marquis and compatible brands, this is the kind of replacement that arrives, drops in, and gets forgotten until the next rinse cycle. The threaded base makes a solid mechanical connection that resists the kind of slow bypass you sometimes see with friction-fit cartridges. Compared to Item 2 above, the trade is a longer body for a sturdier mount.
Strong Points
- 2-inch male thread/MPT base matches Marquis and compatible spas directly
- 35 sq ft media area suits mid-size hot tubs with weekly use
- Two-pack format supports proper rotation instead of over-extending one cartridge
- Cross-compatible with several Cal Spa, Aladdin, and Excel part numbers
Potential Drawbacks
- Threaded base only fits systems designed for that connection style
- Slightly longer body needs a bit more clearance inside the housing
Who Should Grab It
Marquis spa owners who want a reliable aftermarket cartridge at a friendlier cost than dealer parts.
A Better Fit Elsewhere
You run a Jacuzzi, where the POOLPURE PRB50-IN (Item 6) is the right antimicrobial match for ProClarity systems.
The PRB50-IN targets one of the more stubborn problems in hot tub care: bacteria that survive normal rinsing. The antimicrobial trilobal fabric adds a layer of protection between cleanings, which matters in warm water where growth happens fast. For Jacuzzi ProClarity and J-200 series spas, that is a meaningful upgrade over a standard fabric cartridge.
The 50 sq ft media area lands between the compact 25 sq ft and the larger 65 sq ft options in this roundup, making it a strong fit for mid-size Jacuzzi tubs that see a few soaks a week. In our view, the antimicrobial property is most useful in tubs used by multiple bathers or in climates where the cover stays warm for long stretches.
Features That Help
- Antimicrobial trilobal media adds a layer of bacterial resistance
- Direct cross for Jacuzzi PRB50-IN and Unicel C-4950 specs
- 50 sq ft media area balances flow and fine filtration
- Two-pack supports clean rotation without mid-month reorders
Less Ideal Details
- Antimicrobial benefit is most noticeable under heavy bather loads, less so for occasional use
- Sized for specific Jacuzzi models, so cross-brand fit is limited
Feature Snapshot
Perfect Match For
Jacuzzi ProClarity and J-200 series owners who want added bacterial protection alongside standard filtration.
Not Your Match When
Your Jacuzzi uses the smaller 25 sq ft spec, where the POOLPURE PRB25-IN (Item 7) is the right body size.
Smaller Jacuzzi spas need a slimmer cartridge, and the PRB25-IN answers with a 25 sq ft body in the same 5-inch diameter family as its larger sibling. The shorter length lands it in older Jacuzzi models and entry-level spas where the housing cannot accept a 50 sq ft body. For these systems, fit matters more than media area.
Two filters per order also makes this a friendly first purchase for new Jacuzzi owners who want a backup on the shelf. Compared to the antimicrobial PRB50-IN above, the trade is standard trilobal fabric in a smaller body, so the price stays approachable without changing the maintenance rhythm.
Notable Upsides
- Direct replacement for Jacuzzi PRB25-IN and Unicel C-4326
- Two-pack format suits Jacuzzi owners on a tighter maintenance budget
- Trilobal fabric handles bather oils and lotions without clogging fast
- 5-inch outside diameter fits compact spa filter cans
Where It May Fall Short
- 25 sq ft media means more frequent cleaning than the 50 sq ft sibling
- No antimicrobial treatment, so bacterial resistance is lower than the PRB50-IN
Who Will Love This
Owners of smaller Jacuzzi spas with a 25 sq ft spec who want a reliable two-pack without the antimicrobial premium.
Where A Sibling Pick Shines
Your spa accepts a 50 sq ft body, in which case the POOLPURE PRB50-IN (Item 6) extends cleaning intervals and adds antimicrobial media.
This single-pack version of the 5CH-352 is the same cartridge as Item 5, repackaged for shoppers who do not need a rotation pair. The 2-inch male threaded base, the 12 3/16-inch length, and the trilobal fabric carry over directly. For a first-time replacement where the current cartridge is already worn, a single unit makes the most sense.
Marquis owners who already keep a spare on the shelf will find this format useful for topping up. Compared to the 2-pack above, the trade is a lower up-front cost with the understanding that the next order will come sooner. It is a sensible fit for spas used lightly, maybe once or twice a week, where cartridges last longer between swaps.
A Few Highlights
- Same proven 5CH-352 spec as the 2-pack, repackaged as a single cartridge
- Direct fit for Marquis and compatible Cal Spa models
- Trilobal fabric balances flow with fine-particle capture
- Single-pack entry point suits first-time replacement or light-use spas
Things To Weigh
- No spare included, so a second order arrives sooner than the 2-pack option
- Threaded base only fits systems designed for the 2-inch MPT connection
Built With In Mind
Marquis spa owners with light weekly use who want a single cartridge without committing to a 2-pack.
Skip It When
You soak three or more times a week, in which case the 2-pack version of the same 5CH-352 (Item 5) avoids mid-month reorders.
What Matters When Shopping For Pool And Spa Filters
Sizing is the first checkpoint and the one that decides everything else. Measure the length, outside diameter, and end-cap style of your current cartridge, then match those numbers to the spec sheet. A wrong length or a mismatched end cap will not seal, and the pump will push unfiltered water back into the tub.
Media material shapes day-to-day upkeep. Standard paper handles everyday debris and rinses easily. Trilobal fabric adds depth to the filter bed, which captures finer particles and resists clogging during heavy use. Antimicrobial treatments go one step further by slowing bacterial growth on the media itself, useful in warm water with frequent bathers.
Filtration area controls how long a cartridge can work before it needs attention. Smaller bodies, around 25 to 35 sq ft, are common in compact spas and reward weekly rinsing. Larger 50 to 75 sq ft cartridges, like the Unicel C-8411 above, suit bigger pools and built-in spas where longer run times matter.
End-cap style is often overlooked until install day. Open caps with molded gaskets seal differently than closed caps, and threaded bases behave differently from friction-fit designs. Matching the original style avoids leaks and the slow bypass that lets debris circle back into the water.
What To Know Before You Commit
Wrong Turns To Avoid
Ordering by brand alone is the most common slip-up. Two hot tubs from the same maker can use different cartridges depending on model year, so the OEM label only gets you part of the way. Always confirm the part number printed on your current cartridge before clicking through.
Another trap is over-extending a worn cartridge to save a few dollars. A filter that stays in service past its useful life loads up with debris, restricts flow, and forces the pump to work harder. The water may look fine for a day, but clarity slips and sanitizer demand climbs. Replace on a schedule rather than waiting for visible trouble.
When Paying More Pays Off
Higher-tier cartridges earn their keep through media quality and surface area. A 75 sq ft OEM-grade cartridge runs longer between rinses than a 35 sq ft budget option, so the up-front cost spreads across more clean water. Antimicrobial media, like the PRB50-IN above, also cuts down on the chemical adjustments needed to keep water balanced in busy tubs. For a heavily used pool or spa, that premium is easy to justify.
Frequently Asked Questions
How often should pool and spa filters be replaced?
Most cartridges last around 12 months with weekly rinsing and proper water chemistry. Heavily used tubs and pools with high bather loads may need swaps every 6 to 9 months.
Can pool and spa filters be cleaned and reused?
Yes, rinsing with a garden hose every week extends the working life of most cartridges. A deep soak in a filter cleaning solution helps too, though heavily clogged media eventually needs replacement.
What is the difference between Type S1 and Type S2 Intex filters?
They are different sizes built for different PureSpa models. The S1 fits standard PureSpa Jet Massage systems, while the S2 is for slightly larger or newer configurations. Check your owner manual to confirm the right type.
Do all pool and spa filters fit every hot tub?
No, cartridges are sized to specific housings. Length, diameter, and end-cap style all have to match, and brands like Jacuzzi, Marquis, and Watkins each use their own specs. Cross-reference listings help, but measuring your current cartridge is the safest move.
How do I know which replacement cartridge fits my spa?
Pull the current cartridge and read the part number printed on the end cap, then match it against the cross-reference list on the replacement listing. Length, diameter, and end-cap style are the three numbers to confirm.
