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.

Click Here to View Replacement Sand Filters

Click Here to View Replacement Parts for Sand Filters 


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.

Please Click Here to View the Backwash Hose

Please Click Here to View Hose Clamps

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


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 Posted: 6/18/2014 

Have a Hayward sand filter that is only 3 years old on an in-ground pool. When I shut off the pump, water blows out the waste line and I lose prime in the pump rapidly. It doesn't seem to do this on recirculate, only on filter setting. When I test it on recirculate, I do see some small air bubbles slowly coming up in the pump strainer area. It's a Jacuzzi pump and the o-ring and cap look fine. Any suggestions?

InyoPools Product Specialist  Posted: 6/16/2014 

clogged line - Sounds like you have a blockage somewhere. Your skimmer line may be blocked again or you may have a blocked impeller. See our guides on "How To Determine the Cause of Low Water Flow" and "How To Clean Out a Pool Pump Impeller" for further information.

InyoPools Product Specialist  Posted: 6/16/2014 

concerned - If you don't see water going out your waste line while in Filter setting, you are probably OK. To check for sure, see our guide on "How to Replace a Spider Gasket on a Multiport Valve".

Anonymous  Posted: 6/15/2014 

I have one skimmer and that is where I vacuum from. I can close the main drain and the skimmer lines. Other than that I can't tell you if I have another line.
Someone did "unclog" my skimmer line but the debris still doesn't pull into the skimmer. Last year anything floating in the poll, thermometer, noodles..... would end up in the skimmer. Now they do not.
I do am new to in ground pool ownership and not a mechanically inclined female.


 Posted: 6/15/2014 

My house sitter backwash my pool with switching
Switching off the power before changing from
Filter to backwash i know that this is a big no
No i am concerned that ma pool will be damaged how can i establish that all is still well


InyoPools Product Specialist  Posted: 6/9/2014 

nvr218 - Could just be air mixing with the outgoing water. See if there is a leak in the spy glass O-ring. Capture the water going out of the waste line and let it settle. If it is clear, the milking color is just air.

 Posted: 6/8/2014 

curious why my backwash is always milky white...regardless of how long i run it. my pool is crystal clear. same thing happened last year too..HELP ANYONE!!!

InyoPools Product Specialist  Posted: 6/4/2014 

Rookie - It sounds like you are getting air into the suction side of your pump - between the pump and the pool. Try brushing a soapy solution around all your connections between the pump and the pool and see if you can detect bubbles being sucked into a leak.

 Posted: 6/3/2014 

I'm a newbie opening our Inground pool. I'm having trouble getting the hayward self priming pump to prime, it gets close but must be air in the line and loses it again. Of course the cell won't chlorinate as it's not getting flow. The sand filter psi is 23 but when I put it in backwash - nothing happens,nothing flows out. Only have one line coming into the pump from the pool so I cannot isolate the skimmer line. Any ideas what my issue is?

InyoPools Product Specialist  Posted: 6/3/2014 

Vivienne - If you also have little or no flow in "Filter" mode, you may have a badly clogged filter. This could happen if you tried to filter you pool with significant debris in it. Try replacing the top 6" of your filter sand with new sand. If you haven't replaced your sand in 5-7 years, you should replace it now.

InyoPools Product Specialist  Posted: 6/3/2014 

b52 - Assuming you have a separate suction port for your cleaner, it sounds like you have a blockage in your skimmer line. If you shut off the main drain and the suction port, do you have any flow coming to the pump from the skimmer line?

 Posted: 6/2/2014 

There is no water flow when pump is in backwash mode but flows fine when in waste mode? What could be our problem? We did not have a cover and this is our second year with the pool.

 Posted: 6/1/2014 

My pool man just replaced my DE filter with a Hayward sand filter. Now my skimmer doesn't have enough suction when I have both the main drain and skimmer valves open (normal operation). It suctions enough for vacuuming when I have the main drain closed 3/4. Thus during normal operation the debris floating in pool doesn't get pulled into the skimmer. The pool man refuses to comeback and said he refunded my money. Everything worked at closing last season.

 Posted: 5/28/2014 

I am look to purchase the hard hose that goes fron the pump to the sand filter. I have a Hayward pro series pump and sand filter.

InyoPools Product Specialist  Posted: 5/27/2014 

Rho57 - If you had a lot of debris in your pool that went into the filter, you may have to backwash your pool 2 or 3 times to clear that debris. If you don't have a relief valve on the top of your filter, you can open the drain at the bottom slightly to relieve the pressure. Lastly, you may have a bad pressure gauge that needs to be replaced.

 Posted: 5/25/2014 

Our psi is running 25-30 after I backwashed and rinsed. The same as it was before. I have a hayward sand filter and read somewhere that I might need to release pressure but can not find a pressure relief valve at the top of my filter like it said on the web page.

InyoPools Product Specialist  Posted: 5/22/2014 

McKnight - Most filters operate in the 10-20 psi range so yours is acceptable. When yours gets to 25-30 psi, I would backwash it. If you pump is several feet above the pool level, it will drain back more quickly into the pool when the pump is shut off. Some people put a check valve between the pump and pool to stop the backflow.

 Posted: 5/20/2014 

My pressure gauge is staying around 15-20 psi during/after running the pump for 48 hours. Is this a safe "normal" reading? Also, my pump keeps losing prime after just turning the pump off for a very short time to change from filter to another setting (ex: backwash, waste, etc). We just changed the sand this year (first year we have owned the pool, as we just bought the home in December), and found the lateral assembly and center pipe was broken. So of course that was replaced too! What are some reasons the pump keeps losing prime? Thank you for your help! I love this site... it is so helpful!!!

InyoPools Product Specialist  Posted: 5/14/2014 

Julia - Check to see if you are losing water through the "Waste' port while you are in "Filter" mode. If so, your spider gasket in your Multiport Valve may be damaged and would have to be replaced. Otherwise, if you see no other leaks around your pool equipment, the water loss may be just due to evaporation.

 Posted: 5/13/2014 

I have a DE filter with a separation tank. How do I find out which pipe I can use for the waste flow so I can vacuum the pool without clogging up the filter and the bag in the separation tank?

 Posted: 5/13/2014 

I has to backwash my in ground pool because the level became too high after heavy rain. When finished I turned off pump and turned valve to filter. Now my pool is losing water quite fast.
Did I do something wrong?


InyoPools Product Specialist  Posted: 5/9/2014 

nodt22 - Sounds like the VS pump is producing more pressure than your system can handle. Most VS motors have a max speed setting that prevents the motor from generating more pressure than your system can handle.

 Posted: 5/7/2014 

i have a sand filter with a vs pump now i have tried backwashing the filter but the pressure makes the backwash hose blow up i could try low speed but the pump has a delay for low speed. can anyone help

InyoPools Product Specialist  Posted: 4/25/2014 

NDHANSON - I would set the VS Pump at near full speed to increase pressure. It will help raise and then set the sand better.

 Posted: 4/24/2014 

I have a Hayward sand filter and a Hayward variable speed pump. What is the best rpm to set the pump at for backflushing?

InyoPools Product Specialist  Posted: 4/4/2014 

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.

InyoPools Product Specialist  Posted: 4/4/2014 

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.

 Posted: 4/2/2014 

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?

 Posted: 4/1/2014 

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

InyoPools Product Specialist  Posted: 2/9/2014 

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.

 Posted: 2/5/2014 

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

InyoPools Product Specialist  Posted: 1/21/2014 

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.

 Posted: 1/21/2014 

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


 Posted: 12/2/2013 

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

InyoPools Product Specialist  Posted: 11/24/2013 

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.

 Posted: 11/15/2013 

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!

InyoPools Product Specialist  Posted: 9/9/2013 

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.

 Posted: 9/9/2013 

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...

InyoPools Product Specialist  Posted: 8/29/2013 

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.

 Posted: 8/27/2013 

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?