Illustration.
The three types
| Sand | Glass media | Cartridge | |
|---|---|---|---|
| How it filters | Water passes through a bed of filter sand | Same tank as sand, filled with crushed recycled glass | Water passes through pleated fabric cartridges |
| How you clean it | Backwash (reverse the flow to waste) | Backwash | Remove and hose the cartridge |
| Water used to clean | A backwash to waste each time | A backwash to waste each time | Hose water only |
| Replace | Sand, every few years | Glass, less often than sand | Cartridges, every few years |
HealthyWA lists sand and cartridge filters as the common types, and says sand and glass filters are cleaned by backwashing while cartridges are taken out and cleaned by hand, always following the maker's instructions.
When to clean it
Many filters have a pressure gauge: as dirt builds up, pressure rises. Note the reading when the filter is clean; when it rises noticeably above that, clean it. Without a gauge, clean it when the flow back into the pool drops.
How long to run it
HealthyWA says the filter should filter all the pool water within 6 to 8 hours and keep running for at least an hour after the last person gets out. More on pump hours.
How to backwash (sand or glass)
- Turn the pump off.
- Set the multiport valve to BACKWASH.
- Run the pump until the sight glass runs clear, usually a minute or two.
- Pump off, set to RINSE, run 20 to 30 seconds.
- Pump off, set back to FILTER, pump on.
Always switch the pump off before moving the valve handle.
Backwash water goes to waste, so in a hard summer or water restrictions a cartridge filter saves water. Check your local water authority's rules on where backwash water can go.
Common questions
Is a sand filter or cartridge filter better?
Neither suits everyone. Sand and glass are simple and cleaned by backwashing; cartridges save backwash water but need hosing by hand.
How often should I backwash my pool filter?
When the pressure gauge rises noticeably above its clean reading, or the return flow drops.
Is glass media better than sand?
It goes in the same filter tank and is backwashed the same way; makers say it lasts longer than sand. Check your filter's maker approves it.