How To Backwash a Pool Sand Filter

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After a period of time, the contaminates in a sand filter start to clog the sand to the point where water flow is significantly diminished and the pressure gauge rises 8 to 10 psi above normal operation readings. To clean out the contaminates, you have to backwash the sand. This guide shows you the steps in backwashing a filter.

Video

Step by Step

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Step 1

Turn off power to your pool pump at the circuit breaker. To prevent damage to the valve, or any other pool equipment always turn off the pump before moving the multiport valve’s handle 

Step 2

Depress the valve’s handle and turn it until the selector notch points to BACKWASH, then release the handle.

Tip for preventative maintenance: Always turn your valve’s handle the same direction when changing settings; either always right or left. Do not turn opposite direction even if the other way is a shortcut to your desired setting. This reduces chances of uniting the spider gasket and undue wear and tear.

Also, make sure the handle is fully depressed when turning the selector handle.

Step 3

Make sure Waste hose is securely connected to the valve, and free of kinks to allow for free flow to your desired drainage point.

Step 4

Turn on pool pump breaker, then turn on the pool pump. Let he pump run for about two minutes or until the water in the sight glass is free of silt. 

Note: If you;’re planning a longer than normal backwash and rinse due to an excessively dirty filter, set you suction diverter to only pull water from your maindrain. Making this change will prevent your pump from losing prime or running dry if the pool’s water level drops below the skimmer.

Step 5

Turn off the pump again

Step 6

Set the valve to Rinse. Depress the valve selector handle, then turn it to the Rinse setting. After a backwash, sand and debris becomes unsettled settle in the filter’s internal plumbing. The rinse setting returns to the normal path through the filter, flushing debris to waste.

Step 7

Turn the pump on, let it run for about a minute or until the sight glass is clear of silt and sand.

Step 8

Turn off power to pump to set the valve selector handle to its normal Filter setting.

Step 9

Turn on the pump to resume normal filtering schedule. Check your pressure gauge to ensure the system’s pressure has returned to your pool’s normal “clean” PSI range.

If you experience issues after backwashing, here is a list of helpful how-to guides for troubleshooting:

How To Determine Why a Pool Pump Won't PrimeSand in Your Pool?

How to Reduce High Pressure in Your Pool System

How to Correct Low Water Pressure in Your Pool System

Comments

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(1 to 40 of 288)

 Posted: 10/12/2019 

I CANT MOVE THE HANDLE ITS CLOGGED WITH SAND IM AFRAID OF BREAKING THE HANDLE
 Reply

InyoPools Product Specialist  Posted: 10/14/2019 

If the valve is caked with sand, I suggest removing the top handle assembly. The valve cover is held in place with 6 to 8 screws; once you remove them, you should be able to remove the handle assembly and clean out any debris.
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Anonymous  Posted: 7/29/2019 

My pool will only run In filter mode for about 4 hours and then it starts leaking from the top..any suggestions on what can be wrong
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InyoPools Product Specialist  Posted: 7/30/2019 

If you enter "leaking multiport valve" into Inyo's site search, there a few articles explaining the issue. Give those articles a read.
 Reply

 Posted: 7/29/2019 

Should I do it all again if my psi levels are still high? And not back at the 8-10 psi? What should I do?
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InyoPools Product Specialist  Posted: 7/29/2019 

Yes, try it again. You may need to do a longer backwash and rinse if it has been longer than usual since your last cleaning.
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 Posted: 6/18/2019 

Hi, when I put my filter in backwash there’s no pressure, but when the filter is running there is strong pressure
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InyoPools Product Specialist  Posted: 7/10/2019 

Have you recently replumbed and connected the lines to the filter? Because the symptoms you are describing sound like the pipes are on the wrong ports.
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Anonymous  Posted: 6/13/2019 

When do I add the DE
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InyoPools Product Specialist  Posted: 6/14/2019 

You wouldn't have to because this is a sand filter.
 Reply

 Posted: 6/5/2019 

Thanks guys.....appreciate the help
 Reply

 Posted: 5/27/2019 

Outstanding information glad to have found this site
 Reply

Anonymous  Posted: 5/20/2019 

Whenever I run my filter for more than an hour or so I have to backwash in order to get the flow right again. Once I backwash it starts to work properly again for another hour or so. Then repeat. Any idea why this would happen?
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InyoPools Product Specialist  Posted: 5/21/2019 

Is this a sand or a DE filter?
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 Posted: 5/13/2019 

When doing the backwash and rinse cycles do I need to turn my skimmers off and main off
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InyoPools Product Specialist  Posted: 5/14/2019 

No, those lines need to be open so that the pump can draw water.
 Reply

 Posted: 12/20/2018 

My sand filter sight glass is dirty with algae or something. Wondering if it can be replaced or somehow cleaned. Also wondering about the pressure valve the glass or plastic housing is fogged up so I can't read it. Is that replaceable? Thanks, Steve
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InyoPools Product Specialist  Posted: 1/2/2019 

Hello Steve - The sight glass and pressure gauge can be replaced. What is the make and model of your pool filter?
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Anonymous  Posted: 11/11/2018 

I did a dumb thing the other day while vacuuming my pool. Normally I vacuum it on the “waste” setting, but I must have Ben half asleep and vacuumed the entire pool with it on the “backwash setting” what does that mean, and have I done harm to the system or the filter?
 Reply

Anonymous  Posted: 11/11/2018 

I did a dumb thing the other day while vacuuming my pool. Normally I vacuum it on the “waste” setting, but I must have Ben half asleep and vacuumed the entire pool with it on the “backwash setting” what does that mean, and have I done harm to the system or the filter?
 Reply

InyoPools Product Specialist  Posted: 11/15/2018 

Thank you for contacting Inyo. You probably didn't do any significant damage to the filter. However, all of the vacuumed debris went to the bottom of the sand bed instead of the top. This means that when the system is returned to filter and turned on, all of the debris will blow back into the pool.
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 Posted: 8/7/2018 

Hello Jerry - this issue may not be stemming from your filter but from the pump or plumbing. How is your pressure gauge responding in these situations, is it rising or dropping? Do you see air bubbles in the pump basket causing it to lose prime? If so, then you may have an air leak causing the pressure problems. Is your water green or cloudy? If so, the rise in pressure could be from algae (dead or alive) is quickly clogging the filter causing repeated backwashes.
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 Posted: 7/27/2018 

Hello Dean - You'll need to backwash the filters when the filter gauge rises 10 psi over the clean filter PSI. For example, if your filters are 15 PSI when the filter is clean, they'll need to be backwashed when the PSI is 25.
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 Posted: 7/21/2018 

I have 2 36" filters at work. How often should I backwash?
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 Posted: 7/13/2018 

Hello Vince - The vacuum to waste feature would serve as your "rinse" setting.
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Anonymous  Posted: 5/27/2019 

Thank you
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 Posted: 6/15/2018 

My pool filter valve doesn't have a rinse setting. What can i do when I need to rinse?
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 Posted: 6/8/2018 

Hello Nick - No, you do not need to close the return/outlet when backwashing. You can keep those open.
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 Posted: 6/7/2018 

When you backwash, do you keep the outlet/water return side to the pool closed or open?
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 Posted: 6/5/2018 

I have a sand filter.It has new sand and laterals have been cleaned. When you backwash it has very little pressure, after one minute it will almost stop running. What can be wrong with it.
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 Posted: 5/30/2018 

Hello Joseph - You shouldn't worry about adding more contaminants to the filter when backwashing. The process of backwashing will flush contaminants out of the filter. If you want to bypass the filter, use a chemical called Floc & Vac and vacuum all the debris directly to waste.
 Reply

 Posted: 5/27/2018 

I just bought a sand filter for the first time. The manual says it should run around 8 psi. It is running around 10 psi, though. Back washing and rinsing is not making much of a difference. My water is very cloudy because I neglected the pool this winter. I just got the algae under control. My concern is by back washing with the cloudy pool water, am I just adding more contaminates into the sand? Is there an easy way to backwash and rinse with clean water from a source other than the pool?
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 Posted: 5/15/2018 

There is a small gasket/o-ring where you thread in the sight glass. That may have gone bad and that is why it is leaking.
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Anonymous  Posted: 5/14/2018 

I have water coming out of sight valve when backswashing, what is wrong?
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 Posted: 4/23/2018 

Hello JS - You shouldn't need to close the skimmer when backwashing. The only reason for closing the skimmer would be if you lose so much water that the water level drops below the skimmer when backwashing. If it is a suction style vac, the most common cause of the cleaner not switching ends is lack of suction. This could be caused by a dirty filter, holes in the cleaner hose, or a suction side air leak.
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 Posted: 4/20/2018 

There is a shut off valve beneath my skimmer. Do I turn it off (so that water from the pool doesn't flow) before backwashing? Also, my vacuum goes around by itself but it never seems to get to one side of the pool. Is this a problem? Thanks so much!
 Reply

Anonymous  Posted: 3/30/2018 

Has no-one installed a backwash tank? We have a 500 litre tank. The tap is about 20 cms from the bottom. Backflush into this and the next morning the suspended stuff has all fallen to the bottom and the clean water can now be put back into the pool with a hose pipe. I'm in South Africa which is a water scarce country but I would think that this would be good practice anywhere in the world.
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InyoPools Product Specialist  Posted: 8/28/2017 

Joel - You generally backwash a filter when the pressure gauge reads 10-12 psi higher than the last time you backwashed it. And you generally change the filter sand ever 5-7 years.
 Reply

 Posted: 8/27/2017 

Great video, few question new to the pool world. How often do you run the backwash how often do I change the sand?
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InyoPools Product Specialist  Posted: 8/7/2017 

Anonymous (sand in pool) - You may be seeing the fine sand that is in the new sand. Try backwashing and rinsing a couple of more times to wash out any fine sand. Then check the spider gasket in your MPV. If it is damaged, it may be letting sand into the Filter return when it is in Rinse or Backwash. Then you may have to take the sand out again to check the lateral hub and standpipe for creaks.
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