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What is backwashing and how often should you be backwashing?

Updated: Jul 3, 2021

When you backwash, you are reversing the flow of your pool water back through your filter. Note that cartridge filters do not need to backwash, rather, get on a schedule of spraying your filter with clean water, weekly or depending on use. Then perform a filter cleaner soak monthly. Now back to backwashing. Backwashing helps clean any debris and dirt out through the waste line. This will help your filter system run smoothly. How often to backwash will depend on the use of the pool and the debris, possibly from high wind and storms, that has run through your filter. You want to try and scoop out large debris from wind or storms preventing them from running through your system, as best as you can. A good rule of thumb is to backwash when your PSI is reading 10 PSI above your normal PSI reading.

First, you should determine your pool’s normal PSI on the gauge reading. This should generally be around 10 to 15 PSI. Over time, you will learn your pool’s baseline. Your first indication that backwashing in needed would be a rise in your normal PSI reading. For example, your pool normally reads 11 PSI, but you are noticing it climbing to 21 PSI. You will need to backwash to remove dirt and debris that is preventing the water from flowing freely through your filter. If this does not drop the PSI, you will need to ensure your gauge is working properly. Also, you will need to consider the age of your sand or DE powder. Blog coming soon on how often to replace for your filter.

Another indication backwash is needed, would be weak water flow from your return jets inside your pool. Your pump and filter may be running properly, and your gauge is reading a normal PSI, but water flow is low to the pool.

Lastly, do not add new chemicals prior to knowing you will be backwashing. That will only flush them out of your system and that’s money wasted.

Now... how to backwash.

1. Turn off your equipment.

2. Turn your multiport valve to “backwash”.

3. Turn your equipment back on. Your water should now be leaving through your waste line. (note your water level will drop in your pool during this process. Add water to maintain proper levels). Run this step somewhere around 30 seconds or so.

4. Turn off your equipment.

5. Turn your multiport valve to “rinse”.

6. Turn your equipment back on. Run until you see the water run clear. Again, 30 seconds or so. If you skip this step, dirty water will flow back to your pool causing it to be cloudy.

7. Turn off your equipment.

8. Turn your multiport valve back to “filter”. Note to always turn your valve clockwise. Never go backwards between settings. This will damage your valve over time.

9. Turn your equipment back on. Pay attention to your PSI reading currently. It should be between 10 and 15 PSI. This will become your “clean” baseline.


1. Cartridge filters do not need to be backwashed. Follow the cleaning schedule mentioned above, depending on use of your pool.

2. Determine your baseline PSI for your pool between 10 and 15 PSI.

3. Backwash your sand or DE filter when you PSI starts reading 10 PSI above your normal PSI (your baseline).

4. Backwash if you notice weak flow from your return jets inside your pool, but your pump and filter are running properly.

5. Do not add chemicals to your pool prior to you knowing yo

u will be backwashing.

6. Swim, splash, float and have fun! Enjoy your pool.

As always, every pool is different. Different scenarios, environment and even your equipment can produce different results. The information above may not be suited for everyone. Talk to your pool professional or stop by our store 7 days a week for any questions or concerns.

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1 Comment

Adam Dooley
Adam Dooley
Jun 09, 2021

Great information. I always wondered why I was told to make sure to rinse after a backwash.

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