How To Backwash a Pool Sand Filter

WRITTEN BY:  Inyo Pools

  2.98 out of 5 stars on 26 ratings
(Click on a star to add your rating)

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 241)

Inyopools  Posted: 07/20/2017 10:39 AM  Latest 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  Latest 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  Latest

You do have to add new sand after backwash?

Rob  Posted: 07/20/2017 7:08 AM  Latest

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

Inyopools  Posted: 06/01/2017 11:28 AM  Inyo Product Specialist

Mel - I wouldn't worry about a yellowish sight glass. Water is only seen in the sight glass when it is flowing out of the waste line during backwash and rinse. If the water in the waste line is clear, your site glass is ok.

Mel  Posted: 05/29/2017 16:28 PM 

After backwashing and rinsing, my sight glass is yellowish with a little sand in the bottom. (was clear until about 3 days ago. How do I correct this problem? The water coming out of the backflush is clean and clear as is the rinse water

Inyopools  Posted: 05/25/2017 23:19 PM  Inyo Product Specialist

Suzie - Here's an example of how to hook up a suction cleaner through your swimmer - "How To Set Operate the Zodiac X7 Cleaner Through a Skimmer". And, we don"t sell refurbished equipment. Sometimes we do have scratched or dented sales but infrequently. Look for "Clearance Items" in the class of products you may be interested in.

Susie  Posted: 05/24/2017 8:25 AM 

can you tell me how to hook up my sand filter pump so that I can use it as a pool vacuume too. I have the hose hooked to the intake so that I can constantly sweep the floor with the vacuum upon entry is this correct. Do you all sell refurbished sand filter pumps?

Inyopools  Posted: 05/06/2017 9:11 AM  Inyo Product Specialist

Kate - You don't have to change anything on your system. Just turn off your pump before you change your multiport valve to "Backwash". Then turn it back on. Also, we recommend turning the handle on your multiport valve in one direction each time your change the mode.

Kate  Posted: 05/06/2017 6:51 AM 

Very new to this, do I turn off the refueller' and skinners when I am back washing.

Inyopools  Posted: 05/01/2017 16:02 PM  Inyo Product Specialist

George - It sounds like your spider gasket in your multiport valve is damaged. See our guide on "How to Replace a Spider Gasket on a Multiport Valve". To minimize damage in the future remember to shut off the pump before changing filter modes and only turn the handle in one direction to change modes.

George  Posted: 04/29/2017 11:41 AM 

Why do I have water trickling through my back-wash hose when pump is running on filter is the sand dirty in the filter.

Inyopools  Posted: 03/31/2017 12:37 PM  Inyo Product Specialist

Charlotte - Not sure I understand your question. The only way you could have drained your pool to 8" was to close off all the incoming ports (skimmer and suction line) that went above the water line. Otherwise, your pump would have sucked in air and lost prime. All your water to the pump would then be coming from the main drain below the water surface - and going out the waste line. Also when draining your pool, you would use the "Waste". There is no reason to drain the pool water though the filter in the "Backwash" setting.

Charlotte  Posted: 03/29/2017 16:23 PM 

I have just drained my pool. It won't suck the last 8" of water out. I currently have it set to waste. Can I switch it to backwash from the bottom drain?

Inyopools  Posted: 03/28/2017 13:36 PM  Inyo Product Specialist

nolan6324 - Here is a link to a blog we just published, "Reducing High Pressure In Your Pool System". It may be able to help you. Check the easy issues first, like a bad pressure gauge or too many diverter valves shut off between the filter and the return jets.

nolan6324  Posted: 03/26/2017 20:43 PM 

Good evening, I just bought an Above ground pool at the end of last summer with a Hayward filter. Closed it down for winter, and now I have turned on and Have backwashed several times, but the pressure is around 50 and in the summer ran around 10. This is a brand new filter and pool. I am not real familiar with pools, what do you think is going on? help please.

Inyopools  Posted: 02/02/2017 11:02 AM  Inyo Product Specialist

Tim - You can keep the skimmer and self-cleaning system on while your backwash your filter. The backwashing process does not take that long for the other operations to have an effect.

Tim  Posted: 01/31/2017 20:11 PM 

Thanks so much for providing a great blog. I just moved into a new place that has a pool. I have a lot to learn. Just checking, when backwashing, does it make a difference if there is a self cleaning system that uses jets to push everything to the middle of the pool which then sucks it all up. Should I simply keep the skimmer and self cleaning system off when backwashing?

Inyopools  Posted: 12/05/2016 11:19 AM  Inyo Product Specialist

Ruan - You may have a damaged spider gasket in your multiport valve that is allowing water to flow down the wrong paths. See our guide on "How to Replace a Spider Gasket on a Multiport Valve".

Ruan  Posted: 12/03/2016 2:32 AM 

Hi there if i backwash my swimming pool a few minutes and rinse it and turn to filter a lot of dirty water goes back to swimming pool for about 10 - 20 seconds? im concerned one of the filter fingers may be broken there is sand inbetween the dirt but not much or could the filter have a bit too much sand? before it worked 100% it suddenly started with this problem?

Inyopools  Posted: 11/14/2016 12:12 PM  Inyo Product Specialist

backwashing - You may be backwashing too frequently so your water doesn't get that dirty or you may have a damaged spider gasket. See our guide on "How to Replace a Spider Gasket on a Multiport Valve".

Anonymous  Posted: 11/11/2016 15:29 PM 

When I backwash, there is no dirt going through the sight glass. The water remains clear from the start and I hear an air leak when I'm finished

Inyopools  Posted: 09/13/2016 21:59 PM  Inyo Product Specialist

valbo - It sounds like you problem is the pump not priming. See our guide on "How To Prime a Pool Pump". Also check to see if your pump's impeller is clogged. See our guide on "How To Clean Out a Pool Pump Impeller".

valbo  Posted: 09/10/2016 17:51 PM 

All valves are open and my hose is ready to receive dirty water. I've set to backwash and turned on the pump. No water leaving the filter, pool, anything. Any advise on why and what to do now?

Mister Dave  Posted: 08/10/2016 21:28 PM 

My filter pressure runs 14 psi after a good flush. One return jet to above ground 24' pool. I feel good pressure from the jet about three feet into the pool. When this declines significantly to say a foot from the jet, I figure I am overdue for a backflush. The pressure rise is only about 3. Hayward 100 pound sand, 2-horse pump.

Inyopools  Posted: 07/28/2016 11:34 AM  Inyo Product Specialist

TMK - It sounds like you may have a damaged spider gasket in your multiport valve. See our guide on "How to Replace a Spider Gasket on a Multiport Valve". To prevent damage to the spider gasket, make sure the pump is turned off before changing MPV settings.

TMK  Posted: 07/26/2016 19:06 PM 

When I backwash, and this just started two back washes ago, dirty water also gets sent back into the pool through the jets?!? Anybody know what is wrong?