How Often Should a Cartridge or DE Pool Filter Be Cleaned?

The filter is the one piece of pool equipment that most owners never see working. It sits on the pad, hums along, and gets ignored until the water turns cloudy. By then it has usually been struggling for weeks. If you have a cartridge or DE filter, a regular deep cleaning is one of the cheapest ways to protect the pump, keep the water clear and avoid bigger repair bills.

Every six months, sometimes every three

The working rule for cartridge and DE filters is a thorough cleaning at least every six months. Some pools need it quarterly. Pools under trees, pools next to open desert lots, pools with a lot of swimmers and pools that run long hours all load the filter faster. The Valley's dust and the long swim season mean a filter here does more work than the same filter in a milder climate, and that's one reason the interval shouldn't be stretched.

A cleaning is also not the same as a rinse. Hosing off the outside of a cartridge removes the loose surface debris and leaves the real problem alone. The filter media traps fine particles deep between the pleats, along with body oils, sunscreen and the greasy film that builds up in any pool. Those oils are what really clog it, and water pressure from a hose won't lift them out.

What a proper filter cleaning involves

A real cleaning starts with an inspection, not a hose. The tech looks over the filter, the nearby equipment and the O-rings before anything comes apart. Then the filter is opened, the elements come out, and the tub itself gets drained and cleaned, since sludge settles at the bottom where nobody looks. The elements are cleaned to remove dirt, oils and debris, and the O-rings are inspected and lubricated before everything goes back together.

• Inspect the filter, the equipment around it and the O-rings
• Open the filter and pull the cartridges or DE grids
• Drain and clean the filter tub
• Clean the elements to remove dirt, oils and debris
• Lubricate the O-rings, then reassemble and check for leaks

That O-ring step is easy to skip and costly to skip. A dry, flattened or cracked O-ring is a common reason a filter tank leaks or sucks air, and air in the system makes the whole setup less effective. Lubricating the ring each time keeps it pliable and sealing. When an O-ring is past saving, a good tech will tell you at that moment rather than let it fail on a Saturday afternoon in July.

For DE filters there's one more detail. After the grids are cleaned, the filter needs a fresh charge of DE powder to work properly. If a filter was cleaned but never recharged, it can look finished and still filter poorly. It's worth asking whoever does the work to confirm that part.

Signs your filter is due

You don't have to wait for the calendar. A few things point to a filter that's overdue, and most of them show up well before the water looks bad.

• The pressure gauge on the filter reads noticeably higher than it did right after a cleaning
• Water coming back through the returns feels weaker than usual
• The water is hazy even though the chemicals look fine
• The pump sounds strained, or the automatic cleaner moves slowly
• The cartridges are discolored, matted or stiff when you pull one out

If you notice the pressure reading, write down the number right after a clean. That's your baseline. A gauge that climbs a good way above it is the filter telling you it's full. Ignoring it makes the pump work against a wall, which shortens the pump's life and raises your energy use.

And when cleaning isn't enough

Cartridges don't last forever. Once the pleats are collapsed, torn or caked beyond cleaning, no amount of scrubbing brings them back, and replacement is the honest answer. The same goes for cracked grids in a DE filter. A tech who inspects before cleaning will tell you which situation you're in, and should give you the options and the prices before doing anything beyond the cleaning itself.

At Mountain Ridge Pool Service, weekly customers get two cartridge or DE filter cleanings a year included in the monthly price. For anyone else, one-time filter cleanings start at $100, and that covers the inspection, the tub, the elements and the O-rings. If you're in Surprise, Peoria, Waddell or Buckeye and aren't sure when your filter was last done, call (480) 382-6282 and ask.