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.

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Step by Step


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.

Please click here to view the backwash hose.

Please click here to view hose clamps. 

Step 4

Turn on the pool pump breaker, then turn on the pool pump. Let the 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 main drain. 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 a normal filtering schedule. Check your pressure gauge to ensure the system’s pressure has returned to your pool’s normal “clean” PSI range.

Please click here to view pressure gauges. 
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


(1 to 40 of 294)

 Posted: 4/13/2020 

After shutting off my pump I left my multi dial on backwash. Woke this am to the pool drained down to just below skimmer basket. Did the water drain through gose even though pump wasnt running?

InyoPools Product Specialist  Posted: 4/15/2020 

It likely did not. Are you sure your pump does not have a night or early morning run time scheduled?

Anonymous  Posted: 3/30/2020 

Should my pump be on skimmer or main drain when I’m backwashing or can it be in the middle? Which one should be off/on?

InyoPools Product Specialist  Posted: 3/31/2020 

I would pull from the main drain. Depending on how much water you will be putting to waste, your waterline could fall below the optimal level for the skimmer to operate properly. The main drain will not have that issue

 Posted: 1/11/2020 

Hi, I "backwashed" a pool without turning on the pool pump. Just before that I also mistakenly opened a valve that flooded/overflowed the basket in the pump-lots of water pored out of the closed lid above the basket. Then I closed it. I thought it was the valve that takes water from the pool, but instead I was told its the valve that takes water from the spa that flows into the pool below it. After "backwashing" the pool, I turned the pump back on, but there was no suction being generating in the pool, and the spa jets were barely turning on. the spa water is also an inch lower than before. After a while the pump just shut off. Any suggestions how I can fix this?

InyoPools Product Specialist  Posted: 1/13/2020 

Hello - I am little mixed up in the description of the problem, but it sounds like while backwashing you opened a valve and/or pump lid, now suction is low. If that is incorrect, feel free to correct me.If that description is correct, I believe you have air in your system, either from the water level is low or from opening your pump lid. If you have a DE filter, I suggest opening the air relief until it spurts water. If you have a san filter, the air should eventually expel itself.

 Posted: 10/12/2019 


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.

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

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.

 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?

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.

 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

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.

Anonymous  Posted: 6/13/2019 

When do I add the DE

InyoPools Product Specialist  Posted: 6/14/2019 

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

 Posted: 6/5/2019 

Thanks guys.....appreciate the help

 Posted: 5/27/2019 

Outstanding information glad to have found this site

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?

InyoPools Product Specialist  Posted: 5/21/2019 

Is this a sand or a DE filter?

 Posted: 5/13/2019 

When doing the backwash and rinse cycles do I need to turn my skimmers off and main off

InyoPools Product Specialist  Posted: 5/14/2019 

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

 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

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?

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?

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?

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.

 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.

 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.

 Posted: 7/21/2018 

I have 2 36" filters at work. How often should I backwash?

 Posted: 7/13/2018 

Hello Vince - The vacuum to waste feature would serve as your "rinse" setting.

Anonymous  Posted: 5/27/2019 

Thank you

 Posted: 6/15/2018 

My pool filter valve doesn't have a rinse setting. What can i do when I need to rinse?

 Posted: 6/8/2018 

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

 Posted: 6/7/2018 

When you backwash, do you keep the outlet/water return side to the pool closed or open?

 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.

 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.

 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?

 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.

Anonymous  Posted: 5/14/2018 

I have water coming out of sight valve when backswashing, what is wrong?