Sand filters are cheap and simple, filter to about 20 to 40 microns and are cleaned by backwashing. Cartridge filters catch finer particles (about 10 to 20 microns), use no backwash water and are hosed off by hand. Diatomaceous earth (DE) filters give the finest filtration, down to about 3 to 5 microns, but need DE powder added after each backwash and careful handling.
The filter catches what the sanitizer cannot. Each type trades filtration fineness against maintenance and cost.
Side by side
| Sand | Cartridge | DE | |
|---|---|---|---|
| Filtration | About 20 to 40 microns | About 10 to 20 microns | About 3 to 5 microns |
| Cleaning | Backwash | Remove and hose off | Backwash and recharge DE |
| Water used for cleaning | High | Low | High |
| Media replacement | Sand every 5 to 7 years | Cartridges every 1 to 3 years | DE added each backwash; grids replaced occasionally |
| Upfront cost | Low | Moderate | Higher |
| Best for | Budget, simple ownership | Water conservation, clear water | Clearest water, experienced owners |
Sizing
Check two numbers:
- Rated flow (gpm) must exceed the pump’s maximum flow.
- Filter area (sq ft) for cartridges and DE: larger area means longer between cleanings.
Use our pool pump guide for flow.
Pressure tells you when to clean
Note the pressure gauge reading when the filter is clean. Clean or backwash when it rises about 8 to 10 psi above that baseline, or as the maker advises.
DE handling
DE is a fine powder; wear a mask when adding it and follow local rules for disposing of backwash. Some areas restrict discharging DE.
Clear water also needs balanced chemistry; see pool test kits. Browse pumps and filters.
Common questions
Which pool filter gives the clearest water?
DE filters filter the finest particles, followed by cartridge and then sand.
Which pool filter is easiest to maintain?
Sand needs a quick backwash and media change every several years. Cartridges need hosing off but no backwashing.
How big should my pool filter be?
Its rated flow must exceed your pump's maximum flow. Bigger filter area means longer between cleanings.
Can I add glass media to a sand filter?
Many sand filters accept filter glass or other alternative media; check the filter maker's approval.