How do I backwash my sand filter?

Turn the pump off before you move the multiport valve, every time. Operating the valve with the pump running can damage the system.

How to backwash a sand filter

Turn off the pool pump.
Set the multiport valve to Backwash.
Turn the pump on and let it run for 2 to 3 minutes. Watch the sight glass, or the water flow if your filter does not have one, and continue until the water runs clear.
Turn the pump off again. Do this before moving the valve to the next setting.
Set the valve to Rinse. This settles the sand and clears any remaining debris so it does not return to the pool.
Turn the pump on for 1 to 2 minutes.
Turn the pump off and set the valve back to Filter.
Turn the pump back on. Check that the pressure gauge has returned to its normal reading.

When to backwash

Sand filters generally need backwashing every one to two weeks, and more often if the pool is seeing heavy use or after a storm.

The clearest signal is pressure. A rise of 8 to 10 psi above your normal operating pressure means it is time.

After you backwash

Backwashing lowers your water level and dilutes your chemicals. Test your water and adjust afterwards.

Backwash water usually goes to a waste drain or sewer line. Check that your disposal method complies with local regulations.

More on filters

For DE and cartridge filters, and for troubleshooting problems like dirt returning to the pool after a backwash, read our full guide to backwashing a pool filter.

If you run a salt system, see what kind of filter to use with a salt system.

Still need help?

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