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How do you clean a pool filter?

Updated August 2026

30–45 minutes · Easy DIY

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Clean the filter when the gauge reads 8–10 psi above its clean starting pressure, not on a fixed date. The method depends on the type: hose a cartridge element down pleat by pleat in 30 minutes, or backwash a sand or DE tank until the sight glass runs clear and then recharge the DE grids through the skimmer. Past that 10 psi mark the pump is straining against restriction, turnover drops, and the water goes cloudy even when the chemistry tests perfect.

What you need

Before you start: A pool filter is a pressure vessel. Never unclamp the lid until the pump is off at the breaker and the air relief valve has quit hissing, because trapped air can throw a filter lid hard enough to kill someone standing over it. Handle dry DE powder upwind and in an N95, since it is crystalline silica. Keep the electrical side dry as well: if the pump runs off an old cord or a non-GFCI outlet, fix that before you spend another season standing in water beside it.

Steps

  1. Write down the current gauge reading, then kill the pump at the breaker. A time clock can restart a pump while your hands are in the tank.
  2. Open the air relief valve on top of the filter and wait until the hiss stops completely. Close the skimmer and return valves if your plumbing has them.
  3. Cartridge: release the clamp band, lift the element out, and hose it from the top down with the nozzle at a 45-degree angle, so the spray gets between the pleats instead of packing debris deeper.
  4. Cartridge, two or three times a season: soak the element overnight in a filter cleaner solution to dissolve the sunscreen oils and mineral scale a hose cannot touch, then rinse and let it dry.
  5. Sand or DE: with the pump off, set the multiport to Backwash, restart, and run 2 to 3 minutes until the sight glass runs clear. Stop the pump, switch to Rinse, run 30 to 60 seconds, stop again, and return the valve to Filter.
  6. DE only: recharge the grids immediately after the backwash. Mix the labeled charge, roughly 1 pound of DE per 10 square feet of grid area, into a bucket of water and pour it slowly into the skimmer with the pump running.
  7. Wipe the tank O-ring and coat it with silicone lubricant. Petroleum grease swells the rubber and turns a $12 O-ring into a season of drips.
  8. Reassemble, open the air relief valve, restart the pump, and close the valve once a steady stream of water comes out. Write the new clean pressure on the tank in marker: that number is the baseline for next time.

Or hire it out

A pool service charges $75–150 for a standalone filter cleaning, or folds it into a $120–250 monthly maintenance plan. A replacement cartridge is $30–100 and lasts 2 to 4 years, so most of the savings comes from keeping the element you already own clean.

Done. Now the part everyone skips: doing it again on schedule. Log it in OnOtto and the next reminder for pool filter cleanings sets itself.

Log this task, get the next reminder

Frequently asked questions

How do I find my filter clean starting pressure?

Run the pump 10 minutes right after a cleaning or a media change and read the gauge with every valve in its normal position. Most residential systems settle between 10 and 20 psi. Write that number on the tank in marker, because everything after it is relative: clean at 8 to 10 psi above the baseline. If the needle never moves for a month, suspect a stuck gauge rather than a miraculously clean filter.

Can I backwash a cartridge filter?

No. Cartridge tanks have no multiport valve and no way to reverse the flow, which is also why they waste no water. Cleaning one means pulling the element and rinsing it by hand. If your filter has a lever or dial with Backwash, Rinse, Filter, and Waste positions, you own a sand or DE filter instead, and those get backwashed rather than opened up.

Should I use a pressure washer or dish soap on the cartridge?

Neither. Pressure-washer force tears the pleat fabric and opens channels that let dirt pass straight through, and soap residue foams the pool for weeks. Use a hose nozzle and a purpose-made filter cleaner. A diluted acid rinse belongs only in scale removal, and only after the oils are gone, because acid on an oily cartridge bakes the grime in permanently.

When is the cartridge worn out rather than dirty?

Replace it at 2 to 4 years, or sooner if the pleats look flattened and glossy, the end caps are cracked, or pressure climbs 8 psi within a week of a full cleaning. A new element runs $30–100. Buying a second cartridge and rotating them lets each one dry completely between cleanings, which typically adds a season to both. The full timeline sits on how often to replace a pool filter cartridge.

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