Routine maintenance and cleaning
Backwashing a sand filter
Backwashing cleans the filter by reversing the flow. Done at the right time it restores flow; done too often it wastes water and filters less well.
A sand filter catches dirt in its media. As dirt builds up, pressure on the gauge rises and flow falls. Backwashing reverses the water flow to lift the trapped dirt out of the sand and send it to waste. A short rinse then resettles the bed so the first water after cleaning does not carry dirt back to the pool.
Routine guides describe one part of regular pool care and how to do it properly.
The cue is the pressure gauge, not the calendar. When pressure has risen noticeably above the clean reading recorded after the last backwash, it is time. Backwashing more often than needed wastes water and removes the slight layer of dirt that actually helps sand filters catch fine particles.
The short version
Use the gauge as the cue
Backwash when pressure rises above the clean reading.
Always rinse afterwards
Rinsing resettles the sand and keeps dirt out of the pool.
Not too often
Over-backwashing wastes water and lowers filtration quality.
Backwashing correctly
Switch off
Turn the pump off before changing the valve position.
Backwash
Run until the sight glass shows clear water.
Rinse and return
Rinse briefly, switch off, return to filter and note the new clean pressure.
Good practice
- 01
Record the clean pressure
After each backwash.
- 02
Check the water level
Backwashing removes water.
- 03
Check salt afterwards
In salt pools, backwashing removes salt too.
Common questions
How often should I backwash?
When the gauge rises noticeably above the clean reading, rather than on a fixed schedule.
Why is the water cloudy after backwashing?
The rinse may have been skipped, or the sand may be due for replacement.
Do cartridge filters backwash?
No. Cartridges are removed and cleaned instead.
How much water does a backwash use?
It depends on the filter size and how long it runs. Stopping once the sight glass clears avoids wasting water.
Related pool care guides
- Cleaning the pool waterlineA routine task that prevents the same trouble.
- Telling evaporation from water lossA routine task that prevents the same trouble.
- Cleaning a pool cartridge filterA related check on the same part of the plant.
- Filter sand returning to the poolA related check on the same part of the plant.
This guide sits under pump & filter services. Browse all pool care guides. We look after pools at homes and commercial properties across Dubai.
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Next step
Not sure when to backwash?
Send a photo of your filter gauge and tell us the clean reading. We will help you set a routine.