How To Backwash a Pool Sand Filter

Written by:  Danny Rhodehamel

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.

Tips & Warnings


Step by Step

Step 1

To prevent damage to the plumbing or valve you must first TURN OFF THE POOL PUMP before moving the multiport valve handle. For maximum safety turn off the power at the circuit breaker to the pump.

Step 2

Your pool filter valve is probably at the FILTER setting for normal operation. Depress the multiport valve handle and move it to the BACKWASH setting. To prevent damage to the multiport valve seal, always depress the handle fully before turning.

Step 3

Make sure your WASTE hose is laid out to where you want to dump the waste water.

Step 4

Turn the power back on and run the pool pump for at least 2 minutes. The water in the sight glass on the side of the valve will change from cloudy to clear.

Step 5

Turn the power back OFF.

Step 6

Depress the multiport valve handle and turn it to the RINSE setting. After backwashing, the sand is loose and needs to be reset. Also any dirty water from backwashing has to be rinsed out of the filter to WASTE to prevent it from returning to the pool.

Step 7

Turn the pump back ON and run filtere at the RINSE setting for 1 to 2 minutes.

Step 8

Turn the Pump OFF. Depress the multiport valve handle and turn it to the FILTER setting.

Step 9

Turn the pool pump ON for normal filter operation. Check your pressure gauge to ensure that the pressure has dropped 8 - 10 psi from where it was before backwashing the pool filter.

Comments (1 to 40 of 85)

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User: Inyopools

Aroddey – 50 is way too high for a psi reading. You typically have to clean your filter at 20-30. If you have very dirty water as you indicate, you may have to backwash your filter repeatedly until it is clear. If you still have a lot of debris in your pool, you should get most of it out thru the waste line and not run it through your filter. If your pool is clear and your gauge still reads high, you might have a bad gauge.

User: Inyopools

Gin – You may have a tear in your Multiport Valve Spider Gasket. See our guide on “How to Replace a Spider Gasket on a Multiport Valve” for more information.

User: aroddey

My pool's psi is at 50. I don't know if this is normal... but I have already backwashed..(really green nasty water..) then I rinsed.. but the psi is still at 50. what do I need to do?

User: Gin

I have no pressure to backwash pressure is perfect till I try backwash what could my problem be and how do I fix it?

User: Inyopools

Barb - You vacuum line may be sucking air. If you are not losing prime in your pump, you may be building up an air pocket in your filter. Check for air leaks in your vacuum hose by holding the entire length under water while the vacuum in on. If you maintain pressure, you have a leak in your hose. Check the hose connections first then take out sections of hose one at a time.

User: Barb

Just wondering why my pressure gauge rises when trying to vacuum my pool then after 5mins there is no pressure

User: Inyopools

George - Not sure what your end result is. After 2-3 days, is the sand gone? Does this happen every time you backwash/rinse? If you recently changed you sand, you may have fine sand in the new sand that gets through the filter. Try vacuuming the sand to the waste port. Also check the spider gasket in your multiport valve to see if it's damaged and is leaking water into the wrong ports.

User: George

Can anyone please assist me.
Sand blowing back into my pool.
After vacuuming, i backwash, rinse and then when i switch the pump on again, sand blows back in the pool.... (this is a new thing)
ive also noticed when i vacuum the sand up, it already starts blowing back into the pool.. after 2 or 3 days the water is crystal clear again... but irritating...
Thank you
George Cape Town

User: Spider

Have a wuring noise at the top of the sand filter coming from the Multport valve handle.

User: Inyopools

Sonia - It sounds like your pump is not priming. If you do not see water flowing in the pump strainer basket, your pump is not sucking water from the pool. See our guide on "How To Prime a Pool Pump" for further instructions.

User: Sonia

Hi, my inground pool has not been use for 2yrs. Now just cleaned & refilled water. Then I started the backwash, but I see nothing happen but the pump is making sound. It's 5 yrs old sand filter. What should I do? Thanks!

User: Inyopools

Lee - Check the spider gasket on your multiport valve to make sure it wasn't damaged. See our guide on "How to Replace a Spider Gasket on a Multiport Valve". Make sure you turn off the pump every time you change the valve setting or you can blow the spider gasket. Also after you backwash, go to a rinse cycle before switching to "Filter" to rinse out any dirt still in the sand after backwashing.

User: Lee

I have dirt coming up through all my pop ups. I pulled the filter cover off and changed horrible looking sand. I had a beautiful pool for one day and it started blowing dirt again. The laterals looked ok. I'm dumbfounded. I'm new to pool ownership. The buying process took two months and I never saw this pool but blue until it was my turn to do the maintenance. I need help...

User: Inyopools

Jaynie - It sounds like you need a bigger filter. A bigger filter would go longer between backwashes and would keep your pool cleaner. Another option to backwashing is to convert to a cartridge filter. You clean these by pulling the cartridge out and washing it down with a hose. Less water. See our guide on "How to Replace a Pool System DE filter with a Cartridge Filter". Sand filters are like DE filters in installation.

User: Jaynie

This is a very useful page, thanks! Could you answer another question?
when our pool is quite dirty, say after a few days out of town, our pump gains pressure and loses pumping power very quickly after vacuuming, as if it can't cope with too much dirt. To get the power back i have done two backwashes in 12 hours. This loses our pool a lot of water and seems very excessive. Is this this the right method? If i leave the pump running for a day or two will the pumping power come back?

User: Inyopools

Mikedb007 - When you used the "Filter " setting, you probably "set" the sand like you would have in the "Rinse" setting except the rinsed water went back into the pool instead of the waste line. It won't hurt to "rinse" the sand again but you may be past that point. If you can, try vacuuming any debris in the bottom of the pool to the waste line, otherwise keep running in filter mode until the debris is filtered thru the filter.

User: Mikedb007

Thanks for your How-to. I wish I read it before and not after backwashing for the first time.
The pool is not new but we are new owners. It has a Hayward sand filter with top-mount multi-port valve.
I missed the rinse step after backwashing and went straight back to filter(at least I know enough to shut pump off while switching settings). Well we wound up blowing sand and other dirt back into the pool. I have vacuumed on filter setting but it still seems cloudy. I am unsure whether I should be running it on rinse now to set the sand or if it is too late for that. Any ideas on what I can do to get the pool clear in a hurry(supposed to have family over tomorrow for pool party) and do I need to do anything with the pump/filter to make sure it is working properly? Thanks in advance for your help.

User: Inyopools

MPV sequence - That is correct. After vacuuming on waste, clean out any debris in the pump strainer basket and return to the filter cycle. You do not have to backwash because the debris bypassed the filter and went out the waste port.


Hi after vacuuming on waste, do I just empty the drain basket or skimmer I think it's called and go directly to filter after powering off and disconnecting the vacuum and hose?

User: Inyopools

justkeepswimming - Try taking the vacuum off and trying to run the pump in either filter or backwash mode to see if that primes the motor. If not, look for leaks on the suction side of the pump. See our guide on "How to Identify and Correct Air Leaks". If the pump does prime, look for leaks around the suction cleaner hoses.

User: Justkeepswimming

Hi, so I was wondering if I could have your help as well. So I have had my pool for a couple of years now and I got a new pump about a year ago. I got a Hayward Sand Filter and its been doing fine up until recently. There was so much alge in our pump sand we replaced our sand. Then recently we've been trouble it pumping right. We backwash it and we run our vacuum Wanda the Whale and now it won't pump and we can't get it to prime. Please help. Thanks

User: Inyopools

newtopool - Either main drain or skimmer or both is fine. In backwashing you are just reversing the flow of water through the filter - up through the sand instead of down. It does not matter where the pool water comes from.

User: newtopool

Should the pool be set to main drain or skimmer when backwashing?

User: Inyopools

Romegero - There is nothing in the Owner's Manual about waiting a 1/2 hour after Rinse. It just says go to Filter. One of the purposes of the Rinse cycle to repack the sand under water pressure. I don't think sitting for a 1/2 hour without pressure will do much more. And thanks for the suggestion to move Step 6 up in the sequence.

User: Romegero

First, the current Step 6 "Make sure your WASTE hose is laid out..." should probably follow Steps 1 or 2.

My main question relates to a statement in Step 5 "After backwashing, the sand is loose and needs to be reset." I was told after backwashing and rinsing to wait a 1/2 hour before running the pump in Filter mode. This is to allow the sand to settle evenly. Is this true?

I saw in an earlier post that sand should be replaced every 5-7 years. Is that true also for ZeoSand that I use in my filter?

User: Inyopools

hodges - You can expect to lose pressure in backwash. The backwash setting has a shorter pipe path and, therefore, less resistance. As long as you have a strong flow coming out the waste line, you should be OK.

User: hodges

filters fine but looses pressure when i backwash. what is wrong? how high should pressure be when backwashing?

User: Inyopools

Ginny - We have written several How To Guides that may help you. See "How a Multiport Valve Operates" under "Pool Filters" and "How To Set Up In Ground Pool Equipment - Part 1 - Circulation" under "In Ground Pools".

User: joel

HI I have an idoor pool that we are having a few problems with our pump loosing its prime. we have tried a new pump that we loaned and this did the same. the pool level is fine. taps are fully opened.could the sand filter or anything on the pressure side have any thing to do with this or must it be on the suction side.there is no check valve fitted on the suction side so i was wondering if it was building up pressure. could this turn into back pressure on the suction side and empty the pump ?

User: Ginny

I just got a job at a resort cleaning the pools.
We use the Filter/Backwash/Rinse/Filter procedure.
I am confused with how his works in regards to when i need to
turn off the filter button on my machine, and especially when i turn off certain pipes (like the dock side filter/lake side filter and the 1/2 one) i have the other concept down generally

User: Alexandria

inyopools - I think you just solved my problem. I just read your posts regarding high pressure and I think I may have a blockage. We just opened and cleaned the pool. We did NOT use WASTE function to vaccuum the pool with large debris and I believe it is clogged. For the past few weeks the gauge will not drop down below 10 psi, no matter how many times we BACKWASH and RINSE. So just wanted to say thanks for posting. - NEWBIE

User: Inyopools

Frappus - Check to see if your water pressure drops significantly when you run in recirculate mode - bypassing the filter. If it doesn't, you may have a bad pressure gauge that needs to be replaced. If your water pressure drops when you bypass the filter, you may have a blockage in your filter system. If you just opened up your pool and ran very dirty water through your filter instead of out the waste line, you may have a lot of debris yet in your sand or you may have clogged the lateral pipes at the bottom of the vertical pipe in the filter tank. See our guide on "How To Change Sand In a Sand Filter" for more information on checking the laterals.

User: Frappus

I have done multiple backwashes on my salt water pool and the filter gauge is still at 30 psi showing dirty. Can you tell me what I need to do now? The pool and filter is less than a year old.

User: Inyopools

llsunshine32 - This sequence is correct if your filter is due to be backwashed. When you are using the waste port to vacuum debris out of your pool, you are bypassing the sand in the filter, which is correct. No debris is going into the sand during this cycle. So unless you haven't purged your filter for a while, you do not have to go through the backwash and rinse cycles. You can go directly to Filter from Waste.

User: llsunshine32

I have a multiport, top mounted sand filter and my question is in what order do I need to go when vacuuming my pool?

I vacuumed my pool for the first time yesterday and this is what I did:
Turned pump off (of course)
Turned valve from filter to waste, hooked hose and everything up and turned it on and vacuumed until all debris was gone.
Turned pump off and moved valve to backwash, ran it a few minutes
then turned it to rinse, ran it a few minutes
then back to filter
(turning the pump off/on appropriately

User: Inyopools

Wade - Sounds like the spider gasket in the multiport valve is damaged. This gasket provides seal that controls where water goes when you turn the valve handle. If the pump is not shut off when you move the valve handle, you can blow this gasket. See our guide on How a Multiport Valve Operates II for more information. If you have to look at or replace the spider valve, see our guide on How to Replace a Spider Gasket on a Multiport Valve.

User: Wade

I just bought this model pump and filter, and am having a problem with water constantly coming out of the waste port. It sisn't come with a plug to stop it up.

I beleive I have it set up correctly according to Haywards horrible manual.

Any suggestions?


User: Inyopools

jonnytyler - If your pump's strainer basket isn't filling up, you have a water suction problem on the incoming side of your pump. For a list of possible problems and solutions, see our guide on "How To Determine Why a Pool Pump Won't Prime".

User: Jonnytyler

I was wondering? After I back washed my pool
Yesterday I wasn't able to get it to filter. Well at least the water isn't filling up the Cather before the pump. What am I doing wrong

User: InyoPools

Rinse cycle - Leave it on the Rinse cycle until the water shows clear in the sight glass. You are cleaning the sand from the other direction.

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Tips & Warnings

Don't backwash excessively. Contaminates in the sand actually help the filter work more effectively - to a point. Monitor your pressure gauge for an 8-10 psi rise.

Never move the valve handle when the pump is on.

Don't vacuum your pool in backwash mode. You may clog the collection pipes (laterals) at the bottom of the filter.

Please Note:

Inyo Pool Products is not responsible for any injury or damaged equipment
while using our guides. Using our guides is doing so at your own risk.
These guides are suggested use of your pool or spa equipment and may vary
depending on which product you are using.