How often should a pool cartridge filter be replaced?

Plan on about three years, then let the pressure gauge and the condition of the pleats decide. Pentair says that filter cartridge element life will vary with pool conditions such as bather load, wind, dust, etc., and that you can expect an average cartridge life of three years under normal conditions.^[1] That is a planning number, not a deadline.

What shortens or lengthens the life

Heavy swimming, sunscreen, pollen, a pool under trees, a dusty or windy site, and new plaster all load the pleats faster. A lightly used, well-balanced pool lasts longer. Each year of regular cleaning helps, though cleaning is not a cure: it removes the dirt, not the wear.

How you clean matters too. Pentair warns that acid soaking without first removing all oils and cleaner will permanently restrict water flow through the filter and cause the cartridge to fail early.^[1] If you clean cartridges yourself, follow how to clean a pool cartridge filter and keep pressure washers away from the pleats.

The signs it is time

Go by the gauge first. Hayward says that when the pressure rises 7-10 psi above the starting pressure, or when flow decreases below desired rate, clean or replace the filter cartridge.^[2] Pentair says to clean the filter when the pressure gauge reads approximately 10 psi higher than the original starting pressure, or when a significant reduction in flow is noticed.^[1]

Replacement is the answer when:

• Cleaning no longer holds. The pressure is back up within days of a proper wash and soak.
• The pleats are damaged. Torn, flattened, frayed or collapsed pleats let fine dirt pass and cloud the water.
• The end caps or core are cracked.
• The starting pressure after cleaning keeps creeping up. Each clean leaves a higher baseline, which means the media is slowly clogging for good.
• It is simply old. Once a cartridge is well past the three-year planning figure, replace it rather than keep fighting a clogged filter.

Write the clean starting pressure on the filter after every service. Without that baseline, everything above is guesswork.

How a replacement is done

The swap is a few minutes of work once the filter is safely open, and the order is what matters. Turn the pump and any automatic controls off, disconnect power at the breaker, and open the air relief valve until the gauge reads zero. Pentair says to disconnect power at the circuit breaker before servicing the filter.^[1] Then remove the lid and top manifold, lift out each old cartridge, and look at the gasket: the gasket must be firmly and evenly seated around the entirety of the outer lip.^[1] Set the new cartridges on the bottom manifold, refit the top manifold, lid and clamp ring, and bleed the air on restart.

Care with the lid is not optional. Pentair warns that air entering your filter can cause lid separation.^[1] Buy the exact model cartridge from your filter's manual, and use the manufacturer's replacement parts.

Stop and call a pro if

• The gauge will not fall to zero or the air relief valve is blocked. Do not open the filter.
• The tank, lid or clamp ring is cracked or bent. Replace the part before running it.
• The pressure rises quickly even with new cartridges. The problem may be a failing pump, a closed valve or something else in the plumbing.
• The breaker trips or the motor hums. Virginia bars anyone from engaging in, or offering to engage in, tradesman work as defined in § 54.1-1128 without a tradesman licence, unless working under the supervision of a tradesman licensed in that specialty.^[3]
• The filter is old. If the tank itself is aged, a pool service can quote a new filter and pump together.

Getting help in Virginia

If your pump is struggling too, read why a pool pump loses prime, how much a new pool pump costs in Virginia and whether a variable-speed pump is worth it. Browse pool and spa services or more pool and spa answers.

When you are ready, describe your filter once and local pool services quote it.