How to Backwash a Sand Filter

If your pool water has gone cloudy or your filter has lost noticeable pressure, it may be necessary to backwash your filter. If you have a sand filter, this is a fairly simple process accomplish. Out of all the filters, sand filters are the easiest to clean on a regular basis. Instead of having to manually clean the system, you can simply use water from your pool to rinse away dirt, debris, and other contaminants that have started to clog the sand. If you’re experiencing water flow that is significantly diminished and the pressure gauge is displaying anywhere from between 8-10 psi over the starting level, then it’s necessary to backwash your sand filter.

When you backwash your sand filter, the water is discharged through your backwash hose to an area of your choosing, commonly grass or other appropriate areas of the yard. Avoid backwashing into the street or other drainage areas unless you have the okay from your city.

Other times it may be appropriate to backwash your filter is after a large storm, in order to kill an algae bloom, or when trying to treat cloudy water.
Backwashing a sand filter is relatively simple. All sand filters use the same general concept when backwashing, but may have different setups based on model or manufacturer. But here is a general guide on how to backwash a sand filter.

STEP-BY-STEP GUIDE

1) Shut the system OFF. This should always be your first step when working on your pool equipment. This will prevent any damage to the plumbing or the valves. Turn off the power at the circuit breaker to the pump.

2) Unravel the backwash hose, making sure it’s attached securely to your pool filter. Place it where you want the water to drain.

3) After laying down the hose, return to your equipment and find your backwash valve. Your system will either have a push-pull handle or a multi-port valve. If your system has a push-pull handle, one position will either allow the water to flow through the equipment or leave through the backwash hose. Labels on the backwash valve should let you know which. With the system off, move the valve handle into the backwashing position and lock in place. If you have a multiport valve system, your valve will generally have it on a FILTER setting for normal operation. Depressing the valve handle and moving it to the BACKWASH setting will alter this.

TIP: Prevent damaging the multiport valve seal by depressing the handle before fully turning it.

4) Once the handle has been locked in place, turn your system back ON. Water should begin to flow through the hose. Allow the pump to run for approximately 2-3 minutes or until the water runs clear. You can either watch it in the sight glass on the side of the valve changing from cloudy to clear or will notice the water coming out of the hose start to clear up. This is all the dirt and debris getting removed from the filter.

5) Turn OFF your system to stop the backwashing process.

6) At this point (if you have a multiport valve system) you can turn the pump on and set it to RINSE and let it run for a few minutes.

7) Turn OFF the system, depress the valve and return it to the standard FILTER setting.

8) Roll up the hose and remove excess water left from the wash.

9) Turn the system ON and open the air relief valve on the top of the filter. Leave open until the water is consistently released and then close the valve.

10) Check your pressure to make sure it has dropped from 8-10 psi or where it was before you backwashed the system.

That’s all there is to it! You have successfully navigated how to backwash a sand filter. Make sure you check the blog regularly for all kinds of pool and spa maintenance tips!