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.

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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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Anonymous  Posted: 8/9/2012 

When I backwash my Hayward sand filter there is not movement of water anywhere. The eye glass has no water moving around in it. When I put it on rinse...same thing. It just makes a humming noise. I'm worride that I have ruined my sand with drop out chemical. I have used drop out twice now and it does exactly what it's supposed to do, but the returns blow the dirty water right back into the pool?? My pool builder is stumped and we ended up plugging the returns as to not get the waste water back in the pool. NOW i fire the system back up again and we are at cloudy water yet again... I can't help but think my sand has problems. My pool builder said if drop out gets in the sand filter that it sets up like concrete. Is it even possible that the spider gasket can come wrong from the factory? Can anyone help me here? Thanks!

InyoPools Product Specialist  Posted: 8/1/2012 

Hose connections - Yes you need to put an open ended hose on the waste port to drain waste water away from the pump to an area that will take excess water. Check your local restriction. Some municipalities govern where you can discharge pool water. On the hoses from the pump: the top (discharge) port goes to the return port on the pool; the front port going into the strainer basket connects to the pool port going out of the pool.

Anonymous  Posted: 7/30/2012 

I am struggling with figuring out a Hayward S166T Sand filter. Do I put any type of hose on the "waste" nozzel? And where does the backflow go? I am pool dumb. Also, with a hayward 1hp pump. Where do we connect the hoses.

InyoPools Product Specialist  Posted: 7/20/2012 

Backwasher - Sometimes when you are cleaning up an unused pool you use too many chemicals and the pool chemistry goes out of whack. Try using a product called "Pool First Aid - pn 03122. This product has helped many customers eliminate cloudiness and foam. Also if you haven't changed your sand in 6 years, you might consider doing that also.

 Posted: 7/17/2012 

We had a long repair of our pump and so the pool was quite green. It looks better now (after CL and algeacide); however, I can't seem to clear everything during a backwash. I've backwashed for long periods and have rinsed afterwards. The water never runs 'clear'. And, when I put it back to filter, you can see 'white' water coming through the jets so each morning, I'm clearing the 'foam' off the top of the pool again.


InyoPools Product Specialist  Posted: 6/18/2012 

concern - If you have a lot of debris or algae in the pools, vacuum with the filter in "Waste" mode to keep it out of the filter. If you have a relatively clean pool, vacuum in "Filter" mode.

 Posted: 6/17/2012 

Whay setting do I use to vacuum my pool?

 Posted: 6/17/2012 

Do I need to vacuum on waste?

 Posted: 6/3/2012 

All ways wondered if I was backwashing my sand filter right.

InyoPools Product Specialist  Posted: 5/21/2012 

funeeldy - Check to see if you still have an o-ring. If that's not the problem, it may be time to change out the air bleeder.

InyoPools Product Specialist  Posted: 5/21/2012 

Haven't heard that you have to backwash multiple filters one at a time. It is true, however that you should not change your filter setting with the pump on.

 Posted: 5/20/2012 

I have a tagelus pump/filter and the air bleeder is leaking water no matter how tight I make it. When I release it, the water is being pushed out at a high pressure. What am I doing wrong or does the bleeder need to be replaced?

Anonymous  Posted: 5/18/2012 

We have 4 sand filters for our pool. It is my understanding that we can only backwash one filter at a time and to never move the multiport lever to backwash while the pump is on. Is this correct? Thanks.

InyoPools Product Specialist  Posted: 5/15/2012 

If you are just opening your pool and it is full of debris, you may have to backwash several times. Try to get as much of the debris out with a net. Or if you haven’t changed your sand for 5 years, you should do that now.

Anonymous  Posted: 5/12/2012 

i seem to have little pressure after a hour of normal running time

InyoPools Product Specialist  Posted: 4/20/2012 

gayle - I would check your multivalve spider gasket to see if it's damaged and allowing water to flow in the wrong chambers.

 Posted: 4/18/2012 

After backwashing a sand filter, it won't seem to start filtering properly again. E.g. pump tank isn't filling and gurgling and pressure not rising on filter. Any ideas?

InyoPools Product Specialist  Posted: 1/23/2012 

Mae1927 - Tagelus multiport valves before 1993 did not have an air bleeder valve and had to self-purge the air through the return lines. If your valve is 1993 or after, there is an air bleeder valve towards the bottom of the valve next to the lower port - about the size of a quarter. Turn knob counter-clockwise to release air.

 Posted: 1/22/2012 

How do I air bleed on the tagelus deluxe?

InyoPools Product Specialist  Posted: 7/11/2011 

On spewing sand. Sand dumping into your pool usually means you have to replace the spider gasket. Other potential problems are broken laterals and too much sand in your tank. Maintain at least 6" between the top of the sand and the top of your tank.

InyoPools Product Specialist  Posted: 7/11/2011 

On the check valve. Do not remove the check valve. It's there to keep water from backing up in your system when the pressure is off. What filter system you have is not an issue.

Anonymous  Posted: 7/5/2011 

I have a sand filter when i backwash it spews sand into the pool what is going on with this?

Anonymous  Posted: 7/3/2011 

I,m changing from a cartridge system to a sand filter system do I need to remove the check valve that I now have on my system piping?

 Posted: 6/26/2011 

pool has low pressure and when i backwash i see water in backwash glass and leakin out of backwash hose

 Posted: 6/19/2011 

My filter is working fine but the water runs very slowly on backwash???? Any suggestions on how to fix this problem?

 Posted: 6/10/2011 

my vacuum doesn't seem powerful


 Posted: 6/8/2011 

The filter has air - the jet is coming out very slowly. I backwashed, but it sporadically comes out (it usually comes out rapidly). What is wrong? Sand was replaced 3 years ago.

 Posted: 5/23/2011 

filter runs fine but will not backwash, water comes out very slow the same on rinse,

InyoPools Product Specialist  Posted: 9/17/2010 

Changing the sand in a pool sand filter will vary depending on the use of your swimming pool, but on average it is changed ever 5-7 years.

Anonymous  Posted: 9/17/2010 

Thanks didn't know. How often do you change the sand?