Pool filter cleaning

A robot takes the vacuuming off your list. It does not touch your filter, and a neglected filter undoes most of the benefit, because water that is not being properly filtered stays dull no matter how clean the surfaces are.

Know your baseline pressure

This is the single most useful habit in pool maintenance and almost nobody does it. Right after you clean the filter, look at the pressure gauge and write the number somewhere permanent, on the equipment housing in marker is fine. That is your clean baseline.

From then on you are not guessing. When the gauge sits roughly 25 kPa, about 3 to 4 psi, above that baseline, the filter needs attention. This replaces every rule of thumb about how often to clean, because it responds to how dirty your pool actually gets.

Cleaning a cartridge filter

1. Turn the pump off and release the air-relief valve on the filter housing.
2. Open the housing and lift the cartridge out. Note which way up it sits.
3. Hose it down with a fan nozzle, working top to bottom, angling into each pleat. Take your time and get right into the folds, that is where everything hides.
4. Soak it if it is due. Two or three times a year, or any time hosing does not bring the pressure back down, soak the cartridge overnight in a filter cleaning solution to break down oils and scale. Rinse thoroughly afterwards.
5. Inspect before refitting. Look for torn fabric, flattened pleats or a cracked end cap. A damaged cartridge lets everything straight through and is a common reason a pool will not clear.
6. Refit, close up, purge the air and restart. Note the new pressure. If it has not returned close to baseline, the cartridge is likely at the end of its life.

Backwashing a sand filter

Sand is a different job. You backwash rather than remove anything: reverse the flow to lift the bed and flush trapped debris out the waste line.

1. Stop the pump before touching the multiport valve. Moving it under pressure can wreck the internal gasket.
2. Set to backwash, restart, and run until the sight glass runs clear, usually one to three minutes.
3. Stop, set to rinse, run thirty seconds or so to resettle the bed.
4. Stop, return to filter, restart, and top the pool up. Backwashing sends a decent volume of water down the drain.

Sand itself does not last forever. Every five to seven years the grains wear smooth and stop trapping fine particles, and no amount of backwashing fixes that. If the water stays slightly dull despite correct chemistry and clean equipment, aged sand is a likely culprit.

What the robot's own basket needs

Rinse it after every cycle, not when you remember. Debris left sitting in a damp basket dries into a mat that restricts flow and makes the next clean worse, and on some models a blocked basket makes the machine work harder and shortens the motor's life. It takes about a minute under a hose.

Common questions

How often should I clean a pool cartridge filter?

Hose it out every four to six weeks through swimming season, and give it a proper chemical soak two or three times a year. The real trigger is pressure: when the gauge reads about 25 kPa (roughly 3 to 4 psi) above its clean baseline, it is due regardless of the calendar.

Does a robotic pool cleaner replace filter maintenance?

No. A robot has its own basket that catches what it picks up, which takes load off your filter, but your filtration system still processes the whole pool volume and still needs cleaning on the same schedule.

What does pool filter cleaner actually do?

It dissolves what hosing cannot shift: body oils, sunscreen, and mineral scale bound into the pleats. Water alone removes loose debris but leaves the oily film that gradually blinds the fabric, which is why a cartridge that looks clean can still read high pressure.

Can I use a dishwasher or pressure washer on a cartridge?

Do not. A pressure washer drives water between the pleats hard enough to tear the fabric, and dishwasher detergent leaves residue that foams in the pool. A garden hose with a fan nozzle and a proper soak is what the material is designed for.