Equipment and field

Cartridge, DE and Sand Filter Cleaning Steps

Step-by-step cleaning for cartridge, DE and sand pool filters, with pressure cues, safety steps and the mistakes that shorten filter life.

Cleaning a filter is routine work, but the order of steps and the safety steps are where techs get hurt or damage equipment. This page covers cartridge, DE, and sand filters, with the cues that tell you when to clean.

Read the pressure first

Every filter has a clean starting pressure. Record it the day you clean or install media. A common rule from manufacturers is to clean when the gauge reads about 8 to 10 psi above that clean number. Your maker's manual wins if it says something different.

For example, a filter that starts clean at 15 psi gets attention at roughly 23 to 25 psi. If the gauge is broken or stuck, replace it, because every later decision depends on it.

Safety before you open anything

A filter tank holds pressure. Opening it under pressure can be dangerous.

1. Turn the pump off. If you will work near the motor or the timer, switch off the breaker too.
2. Open the manual air relief valve and let the pressure drop to zero.
3. Close the suction and return valves if the filter sits below water level, so the pool does not drain into the pad.
4. Stand to the side when you release the clamp or lid.
5. If a clamp, lid, or tank looks cracked, warped, or corroded, stop and call the manufacturer or a qualified equipment tech. Do not run it.

Cartridge filters

1. After relieving pressure, open the tank and lift out the cartridge or cartridges.
2. Hose each cartridge from the top down, working the nozzle between every pleat. Angle the spray so debris leaves the pleat instead of pushing deeper.
3. Look for oil. A greasy film from sunscreen or lotion will not rinse out. Soak in a cartridge cleaner and follow its label for time and dilution.
4. Look for scale. White crust on pleats points to hard water or high pH. Some techs soak in a dilute acid solution. If you do, follow the product SDS, add acid to water in a plastic container in open air, wear gloves and eye protection, never combine it with chlorine or a cleaner, and rinse until no residue remains.
5. Let it dry in shade and inspect. Replace cartridges with cracked end caps, flattened or frayed pleats, or a fuzzy look that does not rinse away. Filters in that condition pass debris back to the pool.
6. Check the O-ring. Clean it, lubricate it with a pool-safe lubricant, and replace it if it is flat or cracked. Do not use petroleum jelly.
7. Reinstall, close the tank, open the air relief valve, start the pump, and close the valve once a steady stream of water comes out. Record the new clean pressure.

Rotating two spare cartridges on a customer's pool saves time on site. Swap the dirty one, take it back to the yard, and clean it there.

Sand filters

1. Turn the pump off before you move the multiport valve. Moving it with the pump running can damage the valve's internal seal.
2. Set the valve to backwash, start the pump, and watch the sight glass. Run until the water looks clear, which is often a couple of minutes. Follow the manual.
3. Turn the pump off, set the valve to rinse, start the pump for about 30 seconds, and turn it off again.
4. Return the valve to filter, start the pump, and record the pressure.

Where the backwash water goes matters. Some areas restrict discharge to storm drains, neighbors' yards, or streets. Check your local rules and the customer's property.

If pressure stays high after a backwash, the sand may be channeled, or calcium or oil may have bound the media. A sand filter cleaner used per its label can help. Sand does wear out. Manufacturers suggest replacement after several years, and the interval depends on the media and the pool. Check the manual for the filter model.

DE filters

1. Relieve pressure and open the tank per the steps above.
2. Backwash. Then pull the grids or the cartridge elements, hose them clean, and check for torn fabric.
3. Recharge with the DE amount the maker lists, which is based on the filter size. Mix it into a slurry in a bucket and pour it slowly into the skimmer with the pump running.
4. Wear a dust mask or respirator that the SDS recommends. DE dust is fine and easy to inhale.
5. Do not let DE dump into a drain, sewer, or the pool's plumbing in bulk. Check local disposal and discharge rules.

Cleaning plan for a route

A rotation keeps the work predictable. Say you have 60 accounts and want each filter checked every three months. That is about 20 filters per month, or about five a week. You can fold that into stops with the pressure note, and schedule the extras on days with lighter loads. See weekly pool service checklist for how to record the pressure at each visit.

Hard water leaves scale on filters and everything else. If a customer's filters scale up often, look at the cause with calcium hardness and scale.

If a pump struggles after a clean, the problem may be suction, not the filter. See pump not priming.

Mistakes to avoid

• Moving a multiport valve with the pump on. Turn the pump off first.
• Opening a pressurized tank. Relieve pressure and stand to the side.
• Using a pressure washer on pleats. It tears the fabric you are trying to protect.
• Mixing cleaners. Soak in one product at a time, rinse, and follow the label and SDS.
• Skipping the pressure note. Without the clean reading, every later decision is a guess.
• Reinstalling a dirty or dry O-ring. It is the cause of many air leaks and lost-prime calls.