Clean a pool cartridge filter when the pressure gauge climbs 8–10 psi above its clean starting reading, then rinse the cartridge with a garden hose and reinstall it only after the tank is fully depressurized.
That gauge needle is the whole schedule — not a calendar. Clean when pressure crosses the 8-to-10 psi line or return flow visibly weakens; otherwise the pleats load up, the pump works harder, and you move less water for the same electricity. The steps below follow the Pentair cleaning guide for Clean & Clear Plus filters and Hayward’s cartridge service documentation.
What Pressure Tells You To Clean
The rule is roughly 10 psi above starting pressure, with several manuals narrowing it to 8–10 psi or a noticeable flow drop. Note the gauge reading the day you install a fresh cartridge at normal speed — that’s your baseline.
Two exceptions override the gauge: after heavy bather load, sunscreen, or an algae treatment, pleats clog chemically before pressure spikes, so clean early. If pressure drops instead of rising, the cartridge is usually bypassing water through a tear or the tank isn’t sealing — not calling for a wash.
Shutting Down And Depressurizing Safely
Kill the pump and cut power at the circuit breaker first, since a filter can restart on a timer while your hands are inside it; Pentair’s guide requires disabling timers and automation for exactly that reason.
Relieve pressure completely: open the manual air-relief valve on top of the tank and open the drain or pull the drain plug. If the filter sits below pool water level, close the suction and discharge valves or block the lines against backflow. Never crack a lid, clamp, or lock ring on a pressurized tank.
Removing And Rinsing The Cartridge
Open the housing as your model demands — lock ring, clamp, or counterclockwise locking knob — and lift the cartridge straight out. Force nothing; a stuck lid means pressure or a misaligned gasket.
Rinse with a garden hose and straight-flow nozzle, top down, holding the nozzle at about 45 degrees to push water between the pleats while rotating the cartridge to cover every fold inside and out. Skip the pressure washer — high pressure tears the pleat fabric.
Sunscreen, body oil, and sweat need more than water: Pentair calls for soaking at least one hour in a commercial filter cleaner, or 1 cup trisodium phosphate in 5 gallons of water, or 1 cup dishwasher detergent in 5 gallons of water, then rinsing thoroughly. If you’d rather buy a purpose-made degreaser, the tested cartridge filter cleaners we compared cover which formulas handle oils versus scale.
| Cleaning Step | Spec From The Manuals | Watch Out For |
|---|---|---|
| Trigger point | 8–10 psi above clean pressure | Also clean after heavy oil load |
| Hose rinse | 45-degree nozzle, top to bottom | No pressure washers |
| Degreasing soak | 1 hour in commercial cleaner | Rinse fully before reinstalling |
| Acid soak | 1:20 muriatic acid, 10 minutes | Gloves, glasses, N-95 mask |
| Tank and seals | Clear debris, seat gasket evenly | O-ring groove collects grit |
| Reinstall | Arrow aligned with inlet | Fully seat the assembly |
Reassembly, Seals, And Restart
Clean the tank, manifold, gasket, and O-ring groove, then press the gasket in evenly so it can’t pinch. On Pentair RP models, align the support-tube arrow with the filter inlet and seat the cartridge assembly fully — a half-seated cartridge leaks dirty water past the pleats.
Close the drain, refill the housing, and restart the pump with the air-relief valve open. Water spits and hisses, then runs steady with no bubbles; close the valve then. A clean cartridge should settle near the original baseline, well below the pre-cleaning reading. Hayward’s service document covers model-specific lid and clamp procedures if yours isn’t a Pentair.
When Rinsing Stops Working
A cartridge that won’t return to baseline after a full degrease and rinse is spent, not dirty. Matted pleats, brittle fabric, or any tear means replacement. Cartridges typically last a few seasons with regular cleaning, and a torn one passes debris into the pump and heater.
Common Questions
How often should a cartridge filter be cleaned?
Follow pressure, not the calendar. Clean when the gauge sits 8–10 psi above its clean baseline or return flow drops. In a busy swim season that might mean every few weeks; in a light season, far less. A fixed monthly schedule either washes too often or runs too long.
Can I use a pressure washer on the pleats?
No. Both Pentair and Hayward specify a garden hose with a straight-flow nozzle. High-pressure spray opens the pleat weave, tears the fabric, and lets debris into the pump. A hose at a 45-degree angle, worked top to bottom between the pleats, does the job without damage.
Why is the pressure still high after cleaning?
Three usual causes: the cartridge wasn’t fully degreased, the air-relief valve is still open letting air in, or the pleats are worn out. Debris in the O-ring groove or a pinched gasket can also read as high pressure. If a full soak and rinse doesn’t bring it back near baseline, replace the element.
Sources
- Pentair. “Clean & Clear Plus Cartridge Filter Cleaning Guide” Pressure thresholds, hose rinse angle, degreasing and acid soak procedures.
- Hayward. “Cartridge Filter Service and Installation Manual” Housing opening procedures, depressurization, and rinsing guidance.