How To Backwash a Pool Sand Filter

WRITTEN BY:  Inyo Pools

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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.


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 filter 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.


(1 to 40 of 264)

Matthew  Posted: 08/07/2018 12:03 PM 

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.

InyoPools  Posted: 07/27/2018 15:36 PM  Inyo Product Specialist

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.

Dean  Posted: 07/21/2018 16:24 PM 

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

Inyopools  Posted: 07/13/2018 11:36 AM  Inyo Product Specialist

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

Vince  Posted: 06/15/2018 9:55 AM 

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

Inyopools  Posted: 06/08/2018 16:34 PM  Inyo Product Specialist

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

nick  Posted: 06/07/2018 18:55 PM 

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

Jerry  Posted: 06/05/2018 22:12 PM 

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.

Inyopools  Posted: 05/30/2018 17:25 PM  Inyo Product Specialist

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.

Joseph Lawson  Posted: 05/27/2018 8:19 AM 

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?

Inyopools  Posted: 05/15/2018 14:54 PM  Inyo Product Specialist

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: 05/14/2018 12:04 PM 

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

Inyopools  Posted: 04/23/2018 17:13 PM  Inyo Product Specialist

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.

JS  Posted: 04/20/2018 10:59 AM 

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!

Anonymous  Posted: 03/30/2018 9:56 AM 

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.

Inyopools  Posted: 08/28/2017 13:58 PM  Inyo Product Specialist

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.

Joel  Posted: 08/27/2017 21:05 PM 

Great video, few question new to the pool world. How often do you run the backwash how often do I change the sand?

Inyopools  Posted: 08/07/2017 14:41 PM  Inyo Product Specialist

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.

Anonymous  Posted: 08/06/2017 17:18 PM 

I have a Hayward sand filter and I'm getting sand going back to the pool! I have taken the sand and the laterals out to make sure there there's any damage and found no damages. I put everything back and started again but still have sand going into the pool. I am at my wits at help will be a great

Inyopools  Posted: 08/01/2017 12:51 PM  Inyo Product Specialist

Gemo - Try backwashing and rinsing a couple of more time to see if that clears up your sand issue. If not, you may have to remove the sand to check the laterals, the later hub and the standpipe for cracks or other damage.

Gemo  Posted: 07/31/2017 16:19 PM 

Just installed a new MPV. When i rinse after backwash, a seemingly large amount of sand rushes into the glass sight and the waste line. When i switch back to the filter position some sand discharges into the pool. Did i potentially mess up the install? I know the Stem popped off when i removed the old MPV, but i was hoping we would just discharge any sand that got in and then all would be well.

Inyopools  Posted: 07/31/2017 15:41 PM  Inyo Product Specialist

Ga - A cloudy pool is one indication that your filter is not performing well and its sand needs to be replaced. If you don't know when the sand was last replaced, I'd replace the sand. See our guide on "How To Change Sand In a Sand Filter".

Ga  Posted: 07/31/2017 7:33 AM 

Please help I've been to 3 different pool places and no one knows what's wrong with my cloudy (milky) pool water. All my chemicals are testing fine.just bought the house with a SAND pool filter. I'm use to a earth filter is my pool water cloudy cause I need new sand,the pool is probably about 7 yrs. Old and we don't know if they ever changed it. When we opened it the water was green now it's just been cloudy for bout 2 one knows why,

Inyopools  Posted: 07/20/2017 10:39 AM  Inyo Product Specialist

Anonymous (adding sand after backwash) - No, you do not have to add sand after backwashing. You only lose a very small amount of sand during backwash.

Inyopools  Posted: 07/20/2017 10:35 AM  Inyo Product Specialist

Rob - To pump water out of your pool, just set the MPV to "Waste". This mode bypasses the filter. Water flows directly from the pool to the waste port. See our guide on "How a Multiport Valve Operates".

Anonymous  Posted: 07/20/2017 10:07 AM 

You do have to add new sand after backwash?

Rob  Posted: 07/20/2017 7:08 AM 

I have an unground pool with pretty much that same sand filter. We got a lot of rain and I need to pump some water out. What order should I do the backwash, waste and rinse operations?

Susan  Posted: 07/12/2017 9:54 AM 

Thanks you so much for these easy step by step instructions. So clear and easy to use. Prior I was so confused of the exact procedures & now I get it. ??

Inyopools  Posted: 07/10/2017 12:27 PM  Inyo Product Specialist

hope - It sounds like your pump is not priming. Make sure your pool level is high enough so that water is flowing into the skimmer. Then see our guide on "How To Prime a Pool Pump".

hope  Posted: 07/09/2017 13:41 PM 

trying to backwash hayward pool filter but when i turn pump on to filter first, there is no water going through jets and in the basket.

Inyopools  Posted: 07/03/2017 16:30 PM  Inyo Product Specialist

John - No, you only see water flowing in the sight glass when water is going out the waste line.

john  Posted: 07/03/2017 5:30 AM 

is there suppose to be water in the sight glass all the time mine has none

Inyopools  Posted: 06/26/2017 16:22 PM  Inyo Product Specialist

pam - If you have a surge of backwater to the skimmer when you turn off the pump, you may have backpressure building up in the top of your filter tank that impedes water flow as it builds up over time. Check for suction air leaks in the pipe connections at and before the pump. See our guide on "How to Identify and Correct Air Leaks".

Inyopools  Posted: 06/26/2017 12:34 PM  Inyo Product Specialist

Aj - Use the "Waste" mode to purge extra pool water. Using "Backwash" over a period of time would wash away some of your sand. See our guide on "How a Multiport Valve Operates".

pam  Posted: 06/25/2017 12:34 PM 

I have a 1 year old Hayward sand filter. I have to backwash & rinse every 2 days or so only because I don't get the flow in the pool like I should. the pressure only fluctuates 2 psi. it starts back like a champ but 2 days later the water is almost calm.

Aj  Posted: 06/24/2017 9:06 AM 

First time pool owner:
We have had record amount of rain fall lately. The water level is quit high. Can I use the backwash feature to drain the water?

Inyopools  Posted: 06/22/2017 12:22 PM  Inyo Product Specialist

Peanut - It sounds like you have a significant break in one of the filter's laterals, the hub that the laterals go into, or the standpipe coming up from the hub to the top od the filter. You will have to take the sand out of your filter to see this. Seer our guide on "How To Change Sand In a Sand Filter".

Peanut  Posted: 06/20/2017 21:53 PM 

I vacuumed my pool because there was a lot of dirt (sand) and them back washed it and turned it back to filter, I got up today and the whole bottom of my pool is full of sand. what did I do wrong?

Inyopools  Posted: 06/11/2017 21:42 PM  Inyo Product Specialist

Patti - You may have a damaged spider gasket in the MPV. See our guide on "How to Replace a Spider Gasket on a Multiport Valve".

Patti  Posted: 06/09/2017 17:29 PM 

After backwashing and rinse, put it back to filter turned it back on and water is still coming out of there