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How to Backwash a Swimming Pool Sand Filter

What Is Backwashing And Why Is It Necessary? Read on for all you need to know about backwashing a swimming pool filter...


Swimming pool sand filters trap small particles and over time become blocked, requiring a 'backwash' to remove the blockage and resume normal filtration.

An indicator of the need to backwash is a rise of around 5lbs/.35 bar above the clean running pressure. This can be seen on your pressure gauge, which is normally attached to your multiport valve, or the filter lid on some sidemount filters.

How Does Backwashing Work?

Moving the multiport lever to the backwash position reverses the water flow through the sand bed, directing the water and dirt out through the waste port.

The filters' waste port can be permanently plumbed to discharge over a drain, or a backwash hose can be used instead.

The filter is run on backwash for approximately two minutes, and by visually checking the sight glass - you will see the point when the water runs clear, after the dirt has been removed.

Backwashing the filter is recommended as part of your weekly pool maintenance routine.

The Backwashing Process

Follow these steps in order to backwash:

1. Turn the circulation pump off.

Closed position on filter MPV

2. Depress the multiport lever and turn it to the backwash port.

3. Turn the circulation pump back on. Run in this position for approximately two minutes. You will be able to view the dirty water as it passes through the sight glass of the multiport valve. When it runs clear the backwash is complete - this could be more or less than two minutes, depending on pollution trapped in the filter. When backwashing always keep an eye on your water level as you do not want the water level to drop below the skimmer or the circulation system will begin to draw in air. 

4. Switch off the pump and move the lever to the rinse position on the multiport valve.

5. Turn on and run the pump for approximately 15 seconds (to rinse the filter clean) then switch it back off.

6. Return the multiport lever to the filter position and turn the pump back on to resume filtration.

7. If required top up the pool water level.

While recommended weekly, if the pool has high usage, you may need to backwash more frequently. Keeping an eye on your pressure gauge is an essential tool in knowing when to backwash.

Filter position on filter MPV

If you are using a suction pool cleaner it is also recommended backwashing before vacuuming your pool to ensure the suction cleaner will work effectively as well as afterwards to remove any debris trapped whilst vacumming the swimming pool.

If you need any advice on managing your swimming pool, get in touch with us on:

Phone: 029 2070 5059

Email: https://www.allswimltd.com/contactus


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2024 All Swim Catalogue
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All Swim Ltd, Units 3-5 Link Trade Park, Penarth Road, Cardiff CF11 8TQ