Blog | How to Backwash your Swimming Pool Filter.

Water in swimming pools is kept clean by filtration. As we have addressed in other articles on this blog. There are three different types of pool filters. They are Sand, Cartridge, and D.E. Two of these filters require back washing and one (cartridge) requires disassembling to clean. Lets address the sand filter first.

Depending on the type of sand filter there will be a valve either on the side of the filter or the top of the filter. The valve if it is on top will be a multi-port valve.

This valve will have different settings on it. They will usually be Filtration, Backwash, Rinse, Recirculate, Waste and Closed. During normal operation this valve will be set on Filtration. Notice the gauge on the side of the valve. This gauge is how you determine when the filter is dirty and therefore needs back washed. When the pool is first put into operation you should note the reading of the pressure. This will be the clean pressure for your pools operation. When the pressure rises around 10 lbs. over the start-up (clean) pressure it is time to backwash. Back washing is in effect reversing the flow of the water to wash the dirt out of the sand and out the backwash line.

First you need to turn off the pool pump. This stops the water flow to the filter. It is important that you never attempt to move the valve to another setting without turning off the pump. Then if you have a hose for the waste water to run through make sure it is rolled out without any kinks in it. Some of you may have a hard pipe buried that disperses the waste water. After turning the pump off then you will push down on the handle on the valve and spin it to backwash. It will lock in place. Then turn the pump back on. The water will flow out of the hose or pipe. The water should flow for about a minute to a minute and a half. It will start going from a brownish color to more clear. This means it is getting clean. Then you will turn the pump off and move the valve to rinse. Turn the pump back on and let it run for another 30 seconds. This settles the sand in the filter. Then turn the pump off and move the valve back to filtration. Turn the pump back on and note the pressure. It should be back to a lower pressure. The important thing to remember is never turn the valve with the equipment on. The other settings on the filter are "closed" this is for winterizing. Meaning the equipment has been drained and the breakers have been turned off. The "waste" setting is a way to lower the pool water level fast without disturbing the sand. Like if you have a huge downpour of rain and the pool is too full. Recirculate bypasses the filter all together. It may be used if you want to keep the pool water moving but you are having a problem with the filters operation.

Some sand filters have the valve on the side. These filters may have a valve as described above or they may have what is called a push pull or slide valve. It looks like this.

With this valve you just move the handle up to backwash and push it back down for filtration. It requires the same care as the Multi-port valve in its use. Meaning that you need to turn the pump off to move it etc. It only back washes the filter, there are no other settings. If your pool water level is to high you would lower it through back washing.

Lastly we will look at the Cartridge filter. It needs to be disassembled to clean it. It has one inlet and one outlet (other than the drain at the bottom) and no valve. It looks like this.

To clean this filter you need to turn off the pool pump to stop the flow through the filter. Then you will need a wrench to take off the band clamp around the middle. After it is removed you can remove the top of the filter. For ease of cleaning you may want to hose off the grids without removing them. You can remove the bottom drain plug and wash the dirt out through that. The grids can be removed from the filter and hosed off and then replaced if you prefer. After cleaning you will need to reassemble the filter. There is a large o-ring that fits between the two halves of the filter. Make sure it is in place before you put the band clamp back on. When putting the band clamp on it will seat better if you tap on it lightly with a rubber mallet. This assures a more even pressure all the way around as you tighten the nut. After you have it reassembled turn the pump on and check for leaks. If there aren't any you are finished.

All equipment shown here is manufactured by Jandy.