How to Backwash a Sand Filter

Backwashing is the process of flushing out debris caught by a sand filter and essentially “washing” the sand. This process is important to prolong the efficiency and lifespan of a sand filter. In this post we will explore the proper way to backwash a filter along with some backwashing tips and tricks.

The most common question we hear regarding backwashing is “How do I know when to backwash?”

Sand Filter Sand Filter Your pressure gauge is your best friend in this case. A typical starting pressure for a sand filter with fresh sand is 10-12 PSI. When the pressure rises to 18-20 PSI then it is time to backwash your filter. Depending on how dirty your water is, this may occur weekly, monthly, or even just once a season.

If your pressure doesn’t seem to be rising, it doesn’t mean your filter is not working; just your pool does not have a lot of debris. It is important however you only backwash when the pressure rises to this reading. Backwashing too often can be just as damaging as not backwashing at all.

So, your pressure is at 19. What do you do?

First, make sure your filter is off before you make any changes to the valve settings. Next you will need a backwash hose. This is a collapsible hose that usually comes in lengths between 25 and 100 ft.

Make sure your backwash hose is long enough to reach the area where you want to flush the dirty water. Now, attach the backwash hose to the backwash port on your sand filter using a hose clamp.

You can usually tell the backwash port because it will either have a glass eye near the port or it will have a clear hose adapter. These allow you to see the water as it flushes out of your filter. Once the hose is attached, unroll it and lead it out to where you want the dirty water to run.

Now that your hose is set, double check to make sure your filter is off. Next, you are going to move the handle on your multiport valve clockwise from filter to backwash.

The multiport valve is either found on the top or the side of the filter depending on make and model. Make sure you always turn the valve in the same clockwise direction. Turning counter clockwise can cause damage to the gasket under the valve.

Once the valve is set to backwash, you can turn on your pump. Notice the water is now coming out of the backwash hose. Keep watch of the glass eye or clear hose adapter. At first the water will look dirty and brown, however quickly it will change back to clean and clear. Once the water is clean and clear, turn the pump off again.

You are almost done backwashing.

Before turning your valve handle back to filter, make a stop at the rinse setting. Turn your filter back on and run the rinse setting for 10 seconds.

Running your filter on rinse helps to reduce the chances of any sand blowing into the pool after backwashing. This also helps to settle the sand evenly after the agitation of backwashing. Turn your pump off again, move the valve handle clockwise to filter and you're done! Remove your backwash hose and roll it up for next time.

Hopefully you have a better understanding of how to backwash a sand filter. If you have any other questions feel free to stop into one of our stores, call us at 732-955-8288, or hit us up on our web chat down below. We are always ready to answer your pool care questions. Have a great summer!!

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