Pool Filter Cartridge Replacement: When, Why, and Which to Choose

Don't Wait for Cloudy Water

A cartridge filter is the frontline of pool clarity. As pleats load with oils, minerals, and fines, flow drops, pressure rises, and the pump labors. Proactive replacement—before failure—protects the pump, maintains sanitation, and avoids weekend emergencies.

Replacement Triggers

• Time: 12–24 months (residential); 6–12 months (commercial/high bather).
• Pressure: Clean baseline +10 psi = clean; +15 psi = replace soon; +20 psi = replace now.
• Visual: Pleats frayed, separated, or flattened; end caps cracked/brittle; media discolored (brown/gray = oils/minerals).
• Performance: Weak returns, cloudy water despite chemistry, pump cavitation, short cycles.

Three-Step Maintenance (Extends Life 30–50%)

1. Rinse: Garden hose, 45° angle, pleat-to-pleat. No pressure washer (shreds media).
2. Deep Clean: Soak 12–24 hrs in alkaline cartridge cleaner (Natural Chemistry, In The Swim, Jack's Magic). Breaks down oils, sunscreen, scale.
3. Rinse & Dry: Thorough flush; air dry 24 hrs (prevents mold in storage). Reinstall.

Rotate 2 cartridges — always one clean, one in service.

OEM vs. Quality Aftermarket

Aspect	OEM (Hayward, Pentair, Sta-Rite, Jandy)	Aftermarket (Unicel, Pleatco, Filbur)
Price	$40–$90	$18–$45
Media Quality	Standard Reemay®	Equal or heavier (4.0–4.5 oz/yd²)
Pleat Count	Standard	Often higher (more area)
Antimicrobial	Rare	Common (Microban®)
Warranty	1 yr (may void if non-OEM used)	1 yr (manufacturer)
Availability	Dealer / Online	Wide online, pool stores

Check filter manual: most allow aftermarket if specs match. Unicel/Pleatco/Filbur cross-reference tools guarantee fit.

Top Aftermarket Brands

• Unicel: Spun-bonded polyester, sharp pleats, antimicrobial, premium core. 1,000+ SKUs.
• Pleatco: Free-flow core, reinforced pleats, "Free Flow" tech. Made in USA.
• Filbur: Precision pleating, durable end caps, competitive pricing.

Sizing: Measure Twice, Buy Once

Critical dimensions:

• Outside Diameter (OD)
• Length (Overall)
• Top/Bottom configuration (Open / Closed / Threaded / Slip)
• Filtration Area (sq ft) — match or exceed OEM.

Use brand cross-reference tool (Unicel.com, Pleatco.com) with OEM part # or filter model.

Keep Spares — Avoid Downtime

One spare per filter = zero downtime on change day. Bulk packs (4-pack) save 15–25%. Auto-ship subscriptions (online suppliers) ensure you never forget.

A $30 cartridge protects a $500 pump and a $30,000 pool experience. Change it on schedule.