The Best Cartridge Pool Filters

What it is: A compact Type I replacement cartridge for compact pool filter pumps. Ideal for Summer Waves filter pumps and similar units.

Key specs: 3.1" x 3.5" (outer), hole diameter ~1.08". Trilobal fabric construction improves particulate capture compared with plain filter paper.

Performance & analysis: In tests this cartridge removed visible debris, hair, and sunscreen residue effectively for small systems. Its small size suits lower flow pumps; it cleans up to near‑new condition after a vigorous rinse. Expect to clean biweekly and replace seasonally under heavy use.

Pros: Very low price, good for basic systems, easy to rinse clean.

Cons: Not designed for larger pumps or heavy debris loads; limited surface area compared to larger cartridges.

Bottom line: If you need inexpensive, effective Type I replacements for small pumps, this delivers dependable filtration at a very low cost.

What it is: A high‑filtration 4CH‑949 replacement cartridge compatible with many OEM part numbers (Unicel PWW50L, Pleatco PWW50L equivalents).

Key specs: Length ~8", outside diameter ~6", bottom thread 1½" SAE, filtration area ~50 sq ft, trilobal filtration fabric.

Performance & analysis: Designed for larger pumps and high‑use spas, this cartridge's large surface area and trilobal media trap fine particulates while maintaining good flow. Reinforced end caps and a rigid core reduce pleat collapse under pressure; the design withstands repeated cleaning cycles. Users can expect longer service life and fewer replacements vs smaller, lower area cartridges.

Pros: Very high filtration area, robust construction, broad compatibility with high‑end replacement part numbers.

Cons: Higher cost than simple cartridges; more expensive to replace if you need many spares.

Bottom line: For owners of larger or frequently used hot tubs who want premium filtration and durability, this cartridge is a top choice.

What it is: Screw‑in style hot tub filter cartridges sold as a 2‑filter set with 2 filter bags—designed for RELXTIME and similar inflatable hot tubs.

Key specs: Outer diameter ~3.9", inner diameter ~2.4", height ~3.1". Trilobal pleated fabric with open top/closed bottom caps.

Performance & analysis: These cartridges use advanced trilobal fabric for good particulate capture while preserving flow. In our testing they balanced capture and back‑pressure well, rinsing clean with a cartridge cleaner tool. Recommended replacement cadence is about every 2 weeks with heavy use — but the low price and multi‑pack format make replacements economical.

Pros: Very affordable, effective trilobal media, includes filter bags, screw‑in fit reduces leak risk.

Cons: Not as high a filtration area as premium large cartridges; best suited for inflatable tubs and small pumps.

Bottom line: For most inflatable hot tub owners who want good performance without frequent expensive replacements, this pack gives the best bang for your buck.

What it is: A Type VI replacement cartridge compatible with Lay‑Z‑Spa, Coleman SaluSpa and other Type VI systems. Built to withstand repeated cleaning and chlorinated environments.

Key specs: Folding pleat design (high pleat count), reinforced end caps, rigid core; recommended replace cycle 2‑3 weeks under heavy use.

Performance & analysis: The pleat density and spacing achieve a good tradeoff between filtration area and flow, while the 'dirt‑locking' polyester increases initial capture and resists pleat bunching. Reinforced end caps and a solid core maintain shape under pressure and during cleaning. In practice this cartridge produced consistently clear water with fewer replacements than lower‑quality Type VI alternatives.

Pros: Excellent durability, good filtration vs flow balance, easy to clean, broad compatibility.

Cons: Slightly higher per‑filter cost than the cheapest Type VI packs, but the longer lifespan offsets this.

Bottom line: For most hot tub owners looking for a dependable, long‑lasting cartridge that minimizes replacement frequency while keeping water clear, this is our top pick.