How to backwash a sand filter

Need to clean your swimming pool sand filter? Got a high How to backwash a swimming pool sand filterpressure reading on your filter’s pressure gauge? Low pressure from your pool’s return jets? It’s probably time to backwash your filter. This article will teach you how to backwash your swimming pool’s sand filter.

Backwashing a sand filter pushes water through the sand in the opposite direction, causing dirt and debris to be flushed from your filter leaving the sand clean. Your filter should be backwashed at least once a month, or when the filter pressure rises above normal operating pressure.

Backwashing a sand filter is easy, and can be done in minutes.

How to backwash a swimming pool sand filter

1. Check the pressure gauge on your sand filter. If the pressure gauge is reading in the “red”, it’s time for a clean. Some pressure gauges even tell you when it’s time for a clean.

2. Turn off your pool pump, and move the handle on the multiport valve to the “Backwash” setting. (Never ever move the multiport handle when the pump is running!)

3. Ensure any waste line valves are in the open position, and turn the pump back on! Keep an eye on the eyeglass, and when the water runs clear the backwash is complete.

4. Turn off the pump again and move the handle on the multiport valve to the “Rinse” setting.

5. Run the pump again for 15 – 25 seconds, or until the water runs clear again.

6. Turn off your pump, and move the multiport handle back to the “Filter” position, and turn the pump back on. If you opened any valves on the waste line, now is a good time to close those.


That’s all there is to it! Your filter is now clean and ready to keep your swimming pool water clear for another month or so.

Please note: Occasionally after a backwash, you’ll get dirty water back into the pool through the return jets. This can indicate a problem such as: the filter was not backwashed or rinsed for long enough, a suction cleaner was connected during backwash, or there may be damage to the spider gasket / multiport. The pool will clear up quickly and there’s normally nothing to worry about, but it’s probably best to have your system inspected by a pool technician.

After a backwash, it’s always a good idea to test the water or have an electronic water test carried out on your swimming pool water. You may need to add chemicals to the pool and/or top up the water level.