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.


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Susie  Posted: 05/24/2017 8:25 AM  Latest

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?

Inyopools  Posted: 07/19/2016 18:55 PM  Inyo Product Specialist

Judi WV - No, there is no advantage to letting your sand filter sit before backwashing and rinsing. The debris is embedded in the sand. Backwashing lifts the sand up into the top of the tank to separate it and loosen up the debris to be purged out the waste line. Rinsing pushes the sand back down to repack it and remove any loose debris left in backwashing.

Judi WV  Posted: 07/17/2016 16:42 PM 

I am new to using a sand filter. Had DE filter in the past. My question is, is it best to let the filter sit not running for any length of time before backwashing and rinsing in order for debris to settle? It is a Hayward sand filer.

Inyopools  Posted: 07/12/2016 19:39 PM  Inyo Product Specialist

kathy - The sight glass in on the Waste port and only shows flow when the water is going out the Waste post. Check your pump impeller to make sure it is not clogged and restricting good flow. Check your chemical balance and in particular the pH valve. Get your pH value down to 7.4. High pH can contribute to a cloudy pool. If none of these suggestions work, backwash your filter, shock your pool, and run your pump continuously until the pool is clear. Backwash your pool 2 times a day while the pool is clearing.

Inyopools  Posted: 07/11/2016 9:16 AM  Inyo Product Specialist

Jgibson - If you haven't replaced the sand in your filter for a while, you might try that. Or sometimes the pressure gauge itself goes bad and needs to be replaced.

kathy  Posted: 07/10/2016 16:30 PM 

my pool has been cloudy all season. Just changed 150 lbs of sand in my Hayward Sand filter. Still cloudy. 2 days later, I just noticed that the water is not moving freely around like it normally does in the sight glass while the filter is running. The water is just sitting, stagnant in the sight glass. Any idea why the water in the sight glass is not moving around like it usually does while the filter is running?

Inyopools  Posted: 07/08/2016 14:25 PM  Inyo Product Specialist

Leaking backwash - It sounds like the spider gasket in your Multiport Valve may be damaged and is letting water leak into the Waste port. See our guide on "How to Replace a Spider Gasket on a Multiport Valve" to locate and possibly replace this gasket.

Jgibson  Posted: 07/08/2016 11:33 AM 

I have a 15x48 round above ground pool. The pressure gauge on my Proline 94440 Sand Filter hovers around 29 PSI. I have back washed it a few times since opening the pool two weeks ago. However, the PSI has not dropped. Do I need to replace anything?

Anonymous  Posted: 07/05/2016 20:48 PM 

After back washing I placed the valve back in filter mode as always. This time the system continued to slowly fill the hose with water as if I were still back washing. The system continues to remove water from the pool. What should I do to stop this from happening. I am refilling the pool with water. Help

Inyopools  Posted: 07/02/2016 11:21 AM  Inyo Product Specialist

ksmart - In BACKWASH mode the water should come out the Waste port. See our guide on "How a Multiport Valve Operates".

ksmart  Posted: 07/01/2016 19:48 PM 

ok, where is the water supposed to come out when I BACKWASH my sand filter?

Inyopools  Posted: 07/01/2016 13:05 PM  Inyo Product Specialist

Sanmann7 - Make sure your pool chemicals are balanced. Have your pool store check your phosphates level. That can cause cloudiness. Also, backwash and rinse the sand 2-3 more times to clean out the filter.

Sanmann7  Posted: 06/30/2016 12:07 PM 

I have cloudy water after super shocking the green out. Have ran pool pump constantly and clarifier twice but still cloudy ?

Inyopools  Posted: 06/28/2016 12:19 PM  Inyo Product Specialist

john - I think you are referring to the drain plug at the bottom of your sand filter and not sand pump. Check the parts list for you filter to see if you are missing an O-ring or gasket. Click "Replacement Parts"; find your manf and filter model; and look at the diagram of parts around your drain plug.If your model has no O-ring or gasket, try wrapping 4-5 layers of plumber's tape around the threads that the plug attaches to.

john  Posted: 06/27/2016 14:49 PM 

at the bottom back of the sand pump their is a drain plug threaded I have thightened it as far as it will go and their is a leak at the top of the drain plug, no cracks that I can see, I have the right size threaded cap that goes with the pump not sure why its leaking??

Inyopools  Posted: 06/26/2016 13:09 PM  Inyo Product Specialist

jacki - It sounds like the spider gasket in your multiport valve is damaged and is letting waste water into the return port when you backwash. See our guide on "How to Replace a Spider Gasket on a Multiport Valve" to locate and possibly replace this gasket.

jacki  Posted: 06/24/2016 16:48 PM 

How do i backwash without getting the dirty water into my pool after the initial adding of new sand.

Jacki  Posted: 06/24/2016 16:37 PM 

I changed out the sand in my pool this year but when I turn the pump on to Backwash the dirty water from the tank goes into the pool. Do I need to close the inlet valve to the pool before backwashing. I dont want this dirty water in my pool.

Inyopools  Posted: 06/22/2016 10:34 AM  Inyo Product Specialist

closed filter overnight - Your filter is probably alright. I'd check the spider gasket in the multiport valve. See our guide on "How to Replace a Spider Gasket on a Multiport Valve". And your pump may have taken the hit. With no water flow, it had nothing to cool it. Watch for leaks around the pump gaskets and replace them if required.

Anonymous  Posted: 06/21/2016 23:17 PM 

I accidentally left my sand filter in backwash position overnight with ball valve closed on the waste line. Didn't realized until next morning when I realized the pump didn't sound normal. Pump was hot when I corrected the setting back to filter. Could I have damaged the sand filter. Pool water has been cloudy four days now.

Inyopools  Posted: 06/20/2016 14:47 PM  Inyo Product Specialist

Jessica - Do you have any water flow at all? Try putting you multiport valve in Recirculate mode which bypasses the filter. I no or little water flows, your problem isn't the filter. You have a block somewhere in your system. One of the most common system blocks is in your motor's impeller. See our guide on "How To Clean Out a Pool Pump Impeller".