How to Backwash a Sand Filter


Of the three types of filters, a sand filter is the easiest to clean on a routine basis. Instead of manually cleaning the system like you do with a cartridge filter, you use water from your pool to rinse all the dirt and debris out of the filter. That water is then discharged through your backwash hose to an area of your choice. This can be your grass or another area of your yard. Avoid backwashing into the street or other drainage area. Often, your city will have regulations preventing this. If you do not want to backwash into your yard, you can call your city and they can provide information where it is acceptable to backwash to.

“How often should I backwash?” is a typical question asked in Leslie’s locations. A good rule of thumb is to backwash once the pressure displayed on your pressure gauge is 8-10 psi over the starting level. Also, backwashing after cleaning up from a large storm, killing an algae bloom, or when trying to treat cloudy water will keep your filter working effectively.

Backwashing your sand filter is a very easy process. All sand filters use the same concept to backwash, but many have setups that vary due to a different manufacturer or model. The following steps will take you through how to backwash your Sand Filter.

  1. Shut the system off. This should be the case when working with any type of pool equipment.
  2. Unwind your backwash hose, making sure it is tightly clamped to the water outlet.
  3. Once the hose is laid down, return to your equipment and find your backwash valve. Most systems have a “Push-Pull” handle. When the handle is in either position, the water will either flow normally through your equipment or flow out of your backwash hose. Labels on your backwash valve will typically have information on which position your valve needs to be in for backwashing. If there are no stickers, look in product documentation or take a picture of the setup and show a local Leslie’s professional.

NoteSome systems have multi-port valves instead of “push-pull” valves. Instructions on how to set the valve up for backwashing can either be found on the valve itself or in product documentation.

  1. With the system still off, move the backwash valve handle into the backwashing position and lock the handle in place.
  2. With the handle locked in the backwash position, turn on your system. You should begin to quickly see water flowing through the backwash hose.
  3. Continue backwashing for around 3 minutes or until the water appears clear. When looking at the water flowing out of the hose, you may notice it looking dirty. This is the dirt and debris being removed from the sand in the filter.
  4. Turn off the system to stop backwashing.
  5. Roll up the hose, removing excess water that is left from backwashing.
  6. Return the backwash valve handle to its normal position that allows water to flow through your system and lock it in place.
  7. Turn the system on and open up the air relief valve at the top of your filter. Leave this open until water is consistently being released, then close the valve.
  8. Shut off the system.

Products such as Leslie’s Sand Filter Revitalizer can be used in conjunction with backwashing in order to remove caked-on oils and organic materials that are left over after backwashing. Refer to the product instructions for application directions.

If you have any questions about backwashing your sand filter, you can visit your local Leslie’s store to talk to a pool professional.