When a filter needs cleaning
A filter does not need cleaning on a schedule. It needs cleaning when the pressure gauge says so — and the gauge is the one instrument on the pad that tells you before the water does.
- Pressure has climbed 8–10 psi above the filter's clean baseline — the single most reliable signal.
- Returns are weak, or the pool sweep has slowed down.
- Water has gone dull or slightly cloudy while chemistry still tests fine.
- It is pollen season: gauge pressure can rise 5–8 psi in days, and a filter may need attention two to three times a week rather than once.
- The filter has not been opened in a year, whatever the gauge says.
Running a clogged filter does not just cloud the water — it makes the pump work against resistance it was not designed for, which is how a filter problem becomes a pump problem. More on reading filter pressure
What a clean involves, by filter type
The three types fail differently and are serviced differently. Two of them can be backwashed; one cannot be backwashed at all.
Cartridge
Baseline: 12–18 psi when cleanCartridges come out, get rinsed element by element between the pleats, and go back in. A proper clean is not a hose pointed at the outside of the element — debris packs into the folds, and that is the part that raises pressure.
Consumable: Elements wear out and stop sealing. Replacement runs about $150 per cartridge depending on model and how many the housing takes.
Sand
Baseline: set at start-up — record itBackwashed to flush debris out through the waste line, then rinsed to re-seat the bed. Backwashing is maintenance, not a repair — if pressure returns within days, the sand itself is the problem.
Consumable: Sand channels and loses its edge; new media every 5–7 years, $200–$400.
DE (diatomaceous earth)
Baseline: set at start-up — record itBackwashed, then the grids are pulled and washed by hand, and fresh DE is charged back into the filter. Skipping the recharge is why a DE filter can read clean and still pass debris.
Consumable: Grids tear with age; replacement every 5–8 years, $300–$500.
What it costs
A filter clean is quoted after a look at the filter, because what the job is depends on what is actually wrong: a cartridge rinse, a full teardown, or media that has reached the end of its life. You get the number before the work starts.
The replacement parts, where they are needed, are the predictable part. Sand media runs $200–$400 every five to seven years. DE grids run $300–$500 every five to eight. Cartridge elements are about $150 each, and how many a housing takes varies by model. Those are consumables on a known schedule — not surprises.
Or stop tracking it yourself
Filter pressure is checked on every weekly visit, and backwashed or rinsed when the gauge calls for it. Most owners who end up with a badly clogged filter are not neglectful — they simply were not watching a gauge on the side of the house.
Weekly pool service includes that check every visit, along with the rest of the equipment inspection.
Pressure, Media & Frequency
Filter Cleaning Questions
Go by pressure, not the calendar. Clean when the gauge reads 8–10 psi above the filter's clean baseline — for most cartridge filters that baseline is 12–18 psi. In practice that lands most Houston pools at roughly every three to four months, more often through pollen season, when pressure can climb 5–8 psi in a matter of days.
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