How to Backwash Your Pool's Sand Filter

You need to perform regular maintenance, including backwashing the filter, to keep your pool water clean and clear.

Proper backwashing of your pool's sand filter is one way to keep it filtering properly and to ensure it does not build up dangerous amounts of pressure. Sand filters use sand to filter your pool's water instead of cartridges or diatomaceous earth. Over time, the sand gets dirty and compacted, doesn't filter properly and builds dangerous amounts of pressure. When you backwash, water is forced up into the sand, stirring it and cleaning it, while the dirty water is forced out of the backwash line.

Instructions

1. Ensure that your backwash hose or line is placed somewhere appropriate. Some pools have a hard-plumbed line that goes directly to the sewer. Some have a plastic backwash hose that must be manually moved. Place the hose in an area that can handle a copious amount of water, such as the middle of your yard.

2. Turn the filter off, then locate the dial valve. It is the top portion of your filter that has a handle. You should see several labels around the dial valve listing settings settings such as Filter, Recirculate, Waste, Rinse and Backwash. Push down on the dial valve's handle, keeping it held down while you rotate it to the Backwash setting.

3. Turn the filter on. After a few seconds, you should notice water begin to flow out of the backwash line. Let the filter backwash for at least one minute, and more if it has been more than a week since the last backwashing. At first it may be clear water; the dirty water usually does not appear until 20 seconds or more have elapsed.

4. Turn your filter off. Find the Rinse setting on your dial valve and rotate it to that setting. Turn the filter back on and let it run on Rinse for about 30 seconds, then turn the filter back off. The rinse setting pushes water back through the filter, compressing the sand back to its normal state. Failure to rinse after backwashing will result in sand getting into the pool through the return lines.

5. Rotate the dial valve to the Filter setting, and turn the filter back on. Check your pressure gauge. Normal pressure is around 15 to 20 psi on a standard pressure gauge. Any higher and you may need to backwash again. If the pressure is at an optimum level, resume your normal pool routine.

Tips & Warnings

• If using a backwash hose, try to make sure excess water won't be running into the street or road; some neighbors might not like this.

• If your pressure consistently reads high, try turning off your filter. The gauge should read 0. If it does not, it is faulty and not reading correctly.

References

• INYO Pools: How to Backwash a Pool Sand Filter
• Pool Center: Sand Pool Filters