Replace Pool Filter Cartridges

Goal

Replace the cartridge element(s) in a residential pool's cartridge filter. The cartridge is the consumable; even with diligent rinse maintenance, residential cartridges have a 2 - 3 year service life before fibers break down + filtration efficiency drops. Replacement is straightforward but requires the right cartridge for the model.

Prerequisites

• Replacement cartridge(s) matched to the filter make/model (Hayward, Pentair, Jandy, etc. - each has many models)
• New o-ring + lid lube (if the existing o-ring shows wear)
• Bucket + garden hose
• Adjustable wrench or strap wrench for the lid (if stuck)
• 30 - 45 minutes

Verify cartridge count + size before starting. Quad-cartridge filters need 4 matched cartridges; ordering 1 short delays the customer.

Steps

1. Shut off the pump. Verify off at the breaker; some pools have automation that can restart the pump.
2. Relieve filter pressure. Open the air-relief valve at the top of the filter. Wait for hissing to stop.
3. Loosen the filter lid. Most are hand-tightened with a clamp ring or lid-locking ring; some have a screw-on lid. Strap wrench helps with stuck lids - never use a pipe wrench (cracks the lid plastic).
4. Lift the lid. Heavy filters have a lifting handle on the lid; some need 2-person handling.
5. Remove the old cartridge(s). Some filters have a single tall cartridge; others have multiple shorter ones. Note orientation if there's any.
6. Inspect the filter tank interior. Sediment + algae at the bottom = drain + flush the tank with a hose before installing new cartridges. Cracks in the tank = quote a filter replacement (cracks expand over time and a sudden burst floods the equipment pad).
7. Inspect the lid o-ring. Flat, dry, or showing wear → replace + apply silicone lid lube. Don't reuse a marginal o-ring; the cost of a leaking filter is the customer's water bill + your callback.
8. Install new cartridges in original orientation. Seat fully on the manifold.
9. Lubricate o-ring + replace lid. Hand-tighten only - over-tightening cracks the lid.
10. Open air-relief valve. Restart the pump. Watch for the air to bleed out + clear water to start flowing. Close the air-relief valve once water flows steadily.
11. Read the clean-filter pressure. Note it on the field report; this is the new baseline for future "filter dirty" diagnostics.
12. Inspect for leaks at the lid + every fitting for 10 minutes.

Verification

• Filter pump running with no air in the strainer
• No leaks at lid or any pump-to-filter connection
• Pressure reading documented as new baseline
• Customer informed of new pressure baseline (so they recognize "filter needs cleaning" reading later)

Troubleshooting

• Lid won't seal: o-ring not seated OR lid not aligned. Remove, re-inspect, re-lubricate.
• High pressure immediately on startup: cartridge installed wrong-side-up OR cartridge undersized for system. Verify match.
• Air in pump strainer constantly: suction-side leak between pump + filter. Inspect each fitting; tighten or replace.
• Pressure climbs back to dirty-filter range within days: cartridge has a manufacturing defect OR the source of the cloudiness is algae bloom still in the water. Don't re-replace cartridges; address the water issue (see Algae Treatment SOP).

References

• Manufacturer service literature for the specific filter
• Cartridge manufacturer model-cross-reference (Unicel, Pleatco, Filbur)
• Manuall internal: Weekly Recurring Pool Service