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Backwashing Your Pool Filter


Backwashing Your Pool Filter

Why Filters are Backwashed

Backwashing a pool filter is a simple process that is necessary to keep the filter working properly. Both Sand Filters and D.E. Filters need to be backwashed, and we will cover the process for each type here. In normal operation a pool filter is removing contaminants from the pool water and collecting them in the "filter media". The sand itself is the filter media in a sand filter, and D.E. is the filter media in a D.E. filter. Pool filters can only hold so much dirt in the media before it needs to be removed. Just as a vacuum cleaner bag needs to be emptied when it is full, pool filters need to be backwashed when they are full of dirt.

When to Backwash

By regularly checking the reading on the filter pressure gauge, you should be able to determine when your filter needs to be backwashed. As the filter becomes filled with dirt and other contaminants, it becomes harder for the water to flow through it. This will cause the filter pressure to rise. It is a good idea to make a note of the filter pressure when the filter is clean (right after it is backwashed). When the pressure is 6-7 psi above the clean reading, it's time to backwash the filter.

How to Backwash a Pool Filter

Backwashing a Pool Filter is a very easy process. Here are the steps to backwash a filter:

  1. Turn off the pool pump.
  2. Adjust the backwash valve to the backwash position. If you have a push/pull backwash valve ( the vertical piston style valve), you will need to slide the handle up or down as far as it will go. If you have a dial valve (the round valve that has many positions for the handle), push down on the handle and rotate the dial 180 degrees to the postion marked "Backwash".
  3. Turn the pool pump on. Water will come out of the backwash line. After a few seconds the water should become cloudy or even brown and muddy. This is because the dirt in the filter is being pushed out with the water.
  4. Let the system run in backwash mode until the water coming out of the backwash line is clear. This usually takes about 1-2 minutes depending on how much dirt is in the filter.
  5. Turn the pool pump off.
  6. If you have a dial backwash valve (the round style valve), adjust it to the rinse position and run the pump for about 10 seconds to rinse the valve. Then turn the pump off and adjust the valve to the standard "filter" position. If you have a push/pull backwash valve (the vertical piston style valve), skip the rinse step and just adjust the valve back to its "filter" position.
  7. Turn the pool pump on.

If you have a D.E. Filter, you will want to backwash 2-3 times in a row. After each backwash, let the pump run in filter mode for a few minutes. This will allow the D.E. powder to spread out over the grids. Then backwash again. By repeating the backwash a few times, you ensure that all of the D.E. will be removed. After Backwashing on D.E. filter, it will need to be recharged with D.E. please see our section on recharging D.E. filters for more information on how to add D.E.

After the backwash is complete the pump should be returning water to the pool as usual, and the pressure on the filter pressure gauge should be lower than it was before the backwash. It is a good idea to check the backwash line and make sure no water is coming out of it after the backwash. If there is water coming out the backwash line it may mean that the valve is not adjusted all the way back to its correct position.