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.

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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 310)

 Posted: 10/17/2021 

what mixture of sand and peoples do you put into a filter

InyoPools Product Specialist  Posted: 10/18/2021 

First, I would look at your filter manual to see if it is recommended or for or against adding gravel to your pool filter. Generally, it's not necessary to add gravel to your filter nowadays. Most installations I have seen that use pea gravel have enough to cover up the laterals, then fill the rest with sand.

 Posted: 5/17/2021 

When I rinse the pump do I leave open the backwash line or put the cap back on?

InyoPools Product Specialist  Posted: 5/21/2021 

Leave the backwash line open. Water will be coming out of the backwash line during the rinse.

 Posted: 11/24/2020 

Hi I Backwashed my pool yesterday and now it is half empty what happened

InyoPools Product Specialist  Posted: 12/3/2020 

It sounds like you drained your pool. Are you sure you set the valve to Backwash and not Waste or Rinse?

Anonymous  Posted: 5/31/2021 

I had the same problem. My (sand) filter doesn't give me the options or drain, rinse, etc. To backwash, I'm supposed to turn a handle and push down. I've done this before with no problem. This time, I backwashed a little longer than usual and came back out to find the pool down one foot and water gushing all over my back yard. I turned off the backwash. The refill started to kick in, but after a while it stopped and now it's still at the low level. That's my main concern, now. Will it ever refill?

InyoPools Product Specialist  Posted: 6/4/2021 

Turn on the hose again, it would be as simple as that. If you have an autofill that isn't working, just put a hose in the pool and fill it up the old fashion way.

 Posted: 10/15/2020 

Change the sand in filter but noticed every now then on pump start up, sand is pushing back into the pool.. please help.

InyoPools Product Specialist  Posted: 10/19/2020 

When do you notice that sand is entering your pool? Is it usually after a backwash or some other time? If you only see it after backwash, then I would do a more thorough rinse. If there is no correlation with anything else your pool, then I would suspect a cracked lateral

 Posted: 8/26/2020 

when I backwash my pool, do I need to turn off pool filter or leave it on? Also, what's this rinse thing all about and when do I use that, right after I backwash?

InyoPools Product Specialist  Posted: 8/26/2020 

It appears you skipped the guide; see the following excerpts:Step 1Turn 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 6Set 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.

 Posted: 7/1/2020 

We are having trouble with our filter not having much pressure. Please help

InyoPools Product Specialist  Posted: 8/27/2020 

How to Correct Low Water Pressure in Your Pool System or How Do I Correct Low Water Pressure?Pool care topics or questions can be entered into the search at the top of the page to find any relevant guides, articles, or content.

 Posted: 6/11/2020 

Hi, should my pump be on the high or low setting while backwashing?

InyoPools Product Specialist  Posted: 10/23/2020 

The high setting would be preferred for a quicker, more thorough purge of debris.

 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?