How to Backwash a Swimming Pool

Updated February 21, 2017

Swimming pool sand filters remove dirt particles from the pool water and trap them in the sand inside the pool pump. When the sand becomes full of dirt particles, backwashing is needed to remove the dirt. Sand filters must be backwashed when the gauge reading reaches 3.18 to 4.54 Kilogram per square inch (PSI) over the clean reading. When the pressure rises, the filter has to work harder and does not filter the pool water as well.

Turn off the pool pump. Roll out the backwash hose located on the bottom of the tank. Open the waste drain to the hose.

Press down on the multiport valve handle, and turn to "Backwash." If the pump has a slide valve handle, twist to unlock the T-handle and lift up 2 to 3 inches. Open the air bleeder on the filter by pulling out the ring or turning the little screw counterclockwise.

Turn on the pump. Watch the backwash hose. When it fills with water, run the pump until the water in the sight glass runs clear, or for two to three minutes. The sight glass is the little round unit on the side of the tank that has plexiglass so you can see the water running into the waste drain. Turn off the pump. On the slide valve, push the handle down and twist to lock. For the multiport valve, continue to Step 4.

Turn the multiport valve handle to "Rinse." Turn on the pump and run it for 25 seconds. Turn off the pump. Turn the multiport valve to "Filter."

Roll up the backwash hose. Clean out the skimmer baskets. Turn the screw on the air bleeder clockwise to close it. Turn on the pump.

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