How To Backwash a Pool Sand Filter

Written by:  Danny Rhodehamel

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.

Tips & Warnings


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.

Comments (1 to 40 of 156)

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User: Cfran2020

Hello, great video!! I have a Hayward sand filter with 350lbs of sand and a 1.5 hp ecostar Hayward pump. Normal pressure is at 18 psi and has been since installed last October. When pressure reaches 22 psi there is so little water moving you can't really tell the pump is running, once I back flush it drops back to 18 and runs fine. Replaced the gauge to see if that is the issue and same issue. Should a rise in 4 psi be enough to basically shut down flow? You reference a min of 10 psi before back flush is needed several times. Thanks for your help.

User: Inyopools

Mugsy51 - No, there is no lock on the valve that you have to release to depress the handle. Sounds like something is stuck inside the MPV. Try taking the top assembly off of the MPV like you would do to replace the spider gasket to see what might be binding the handle. See our guide on "How to Replace a Spider Gasket on a Multiport Valve".

User: Mugsy51

I've watched your demonstration many times since I have to backwash my Pentair Triton II sand filter for the first time. In your presentation and others it seems like people just push down on the multiport valve and it goes down. I've been trying all afternoon with all my weight, but it just won't budge. Is there some kind of latch or do-dah to fiddle with first?

User: inyopools

louie4 - Sounds like it's time to change your sand. Sand should be changed every 5-7 years. And if the standpipe assembly came up, you will have to pull the sand out anyway to reset the assembly.

User: louie4

My Hayward sand filter is 6.5 years old. I backflush it regularly, but it doesn't seem to get itself clean anymore. There is no change in the pressure drop. Always about 28-29 psi. Thinking I had built up a layer of impermeable debris on top of the sand, I took the top off. Not much debris there. But the standpipe assembly came up through the sand with the top. Now what?
Is it time to drain the filter and replace the sand? Or just figure out a way to get the standpipe back down?

User: Espocom

8-8-2015 My compliments to you on the way you have your website set up. I watched your "How To" on back-washing a sand-filter and found it to be very, very helpful. I'll certain purchase items on-line from you as I get better, more accurate information from your site than the high school kids behind the counter at my local pool store. Thanks again!

User: Inyopools

caitlin - If your filter gauge never showed pressure before and is now stuck on 22 psi before and after backwashing, I would guess that your pressure gauge is bad. And this filter has not air relief valve. Air bleeds naturally through the sand.

User: caitlin


User: Inyopools

Sandrosko - 30psi is high for a sand filter. If you vacuumed a lot of debris through your filter you might try backwashing /rinsing 3-4 time to remove the debris from the sand. If you haven't replaced your sand in 5-7 years, it's time to replace your sand. Your pump may be too large for your filter. The filter size should be large enough to at least handle the GPM water flow generated by your pump. I'd recommend a size larger than required for a buffer and to the time between cleanings.

User: Sandrosko

The pressure during normal filtering had been running at 30psi. When I back wash after vacuuming, water shoots out of the sight glass like a fire hose.

Any ideas?

User: Inyopools

Deeno - If your Mutiport valve is in Waste mode and you forget to open the Ball valve on your waste line, water flow will stop. Any air in the system will be compressed and may blow gaskets. The motor will be running with no water flow to cool it and it will overheat but hopefully shut off through the motor's overload protector.

User: Deeno

Can you tell me what would happen if when you backwashed, you forgot to open the waste valve? Would contaminates somehow go back into the pool because of pressure, or would the sandfilter blow before that happened?

User: Inyopools

Steve - You did not damage your sand filter. When you are in rinse mode, the water is directed down through the sand and up through the standpipe just like in filter mode, but instead of going back to the pool for "filter", it is directed out the waste port during "rinse". See our guide on "How a Multiport Valve Operates".

User: Steve

I accidently vacuumed my pool in the rinse setting. Could I have damaged the sand filter?

User: Inyopools

backwash - You would leave all the valves open for backwash the same as if you were in filter mode.


Hello, before starting a backwash, do i need to close the main valve to the pool, as in when i clean the skimmer box? or do i leave all valves open along the system?

User: Inyopools

swimmerjane - Sounds like the capacitor of your motor is failing. See our guide on "How To Replace a Pool Pump Capacitor" for more information.

User: swimmerjane

Hello there. If we turn off our pool pump for any reason It is difficult to get it to restart. It will hum for about 10 seconds and then shut off. It will reattempt after a few minutes. Sometimes it will engage most times it does not and it will throw the breaker. My husband believes that because we had the skimmer clogged with leaves a couple of times when we were away, it damage the pump. We have the pool pump on a timer to turn on in the morning and off in the evening. Our dealer suggest that this could be hard on the pump - the starting and stopping. Ideas, suggestions?? Pump is only three years old.

User: inyopools

bren A - If you changed anything on your system after last year, look at those changes and make sure they were done correctly. If this is an above ground pool, do you have one of the shut off valve closed preventing water from getting to the pump. If this is an in-ground pool, make sure your diverter valves are set correctly so you have an open path to the pump.

User: bren A

I can't Backflush I get nothing. When I turn back to normal filltration I get nothing again nothing. It was renning perfict last year. It seems the names on the circle indercater is wrong what can I do.

User: Inyopools

Courtney - The normal psi for a Hayward Sand Filter is 10-15 psi. You would normally backwash the filter when the psi is 10 psi higher.

User: Inyopools

New2Pools - Yes water is suppose to flow out of the waste hose on a rinse cycle. See our guide on "How a Multiport Valve Operates" for more information. Question #2 - I would patch the hole in the liner to make sure it doesn't get bigger. Here's a link to our "EZ Patch 28 - Vinyl Pool Liner Repair Sealant".

User: Courtney

What is a normal psi for a Hayward Sand filter and when should I perform a backwash?

User: New2Pools

2 questions....#1-Is water supposed to come out of backwash hose during rinse cycle?.....#2-Have a hole in top of liner, should I be worried about rain water getting in there?

User: Inyopools

jen - 14 psi is good. You usually don't have to clean a filter until it reaches 20-30 psi. This is more likely a pump motor issue. I assume this pool was operational last year and shut down during the winter season. When you say "the whole thing completely shuts off", it sounds like the motor stopped. If so, your may have a voltage problem. If your voltage is too low, the motor will heat up and stop. Check that the wire connections are tight at the motor terminals. Check the line from the pump to the circuit breaker to make sure it was not damaged. Check that you are getting the correct voltage out of the circuit box and into the motor. Should be 115 or 230 depending on your motor configuration. If you have a switch between the circuit breaker and the pump, check its connections.

User: jen

Just opening my in ground pool. Have sand filter. When on filter it runs for about 5 mins or so then whole thing complete shuts off. Could pressure be to high.? It's at 14 psi.

User: Inyopools

Clueless - Not sure what you are referring to when you say "valves". If they are diverter valves that are used to turn off/on parts of the pool, I would say to leave them open while the multiport valve is in backwash mode.

User: Clueless

Sorry of this sounds stupid, but I really don't know what I am doing. This information is great, but I can't get my head around when to open and close the valves to the pool? Should I have both valves open before I star this process and leave them open throughout?


User: Inyopools

Justin J - If you have to backwash that frequently, you are probably way past the time to replace the filter's sand. I would do that first. See our guides on "How To Change Sand In a Sand Filter" or "How To Replace the Sand in a Pentair Triton 2 Side Valve Sand Filter" for further instructions. Then check the spider gasket in your filter Multiport Valve (MPV) to see if it is damaged and is possibly leaking between ports. See our guide on "How to Replace a Spider Gasket on a Multiport Valve".

User: Justin J

I have a couple questions. Why wont my filter backwash unless I run the rinse cycle first. If I go from filter to backwash and turn it back on nothing happens, but if I go from filter, to rinse, and then to backwash its backwashes just fine. Also it seems I have to backwash frequently, like every couple days. THe jets in the pool get weak, suction is weak and the psi is up. SO i backwash and I'm good for another couple days. IS it time to replace the sand and/or filter completely? I recently bought this house so I have no idea how old the equipment is.

User: Mindychua

Im trying to open the pool for the year, and the filter is cycling through power. It'll run normally for a few seconds, then have a burst of power for a few, then back and forth? I tried back washing, but I was worried something was really wrong, so I turned it off. The pool is an absolute mess, and I'm not sure if that has something to do with it. Thanks! I have a video of it would help.

User: Inyopools

Dawn - I also don't understand why your pool continues to fill with water. Your pool is a self-contained system. The extra water has to come from somewhere outside the system like rain or runoff into the pool. Do you have a sprinkler system that is spraying water into the pool?

User: Dawn

My pool continues to fill with water. When I backwash it is barely backwashing. Then when I rinse the gauge rises back up. Pool is now cloudy but mostly concerned why the water level continues to rise.

User: Inyopools

Michelle - You only have to backwash a sand filter when the sand is clogged with decontaminates. You will know this when the pressure gauge on your filter creeps up to 10-15 psi above its normal operational range and your spa starts to look cloudy. With little use, I would doubt that you would need to backwash more than 1 or 2 times a month. Depends on how much outside debris is getting into your spa.

User: Michelle

HI There: We have a spa with a sandfilter at work. Is it necesary to backwash the pool on a weekly basis if no one has been in the spa during that period?

User: Inyopools

BT - See our guide on "How To Go From Cloudy To A Crystal Clear Pool". Also you might want to try a clarifier. This one has good reviews: "Concentrated Clarifier 1 Qt". The sand “puddles” may fine sand getting through the filter, a damaged spider gasket or a broken lateral.

User: BT

Have a new Hayward sand filter and pump. After back washing and rinsing (turning the pump off in between each step), the water going back into the pool doesn't look clean. The pool is clear but has a very slight cloudiness to it. I've shocked and kept up with chlorine tabs in the skimmer, and have vacuumed (there are a few small "puddles" of what looks like sand on the bottom after every few days). Any thoughts?

User: Inyopools

green pool - I would guess the water coming out of the waste port just looks clear because you're not seeing a large volume of it. Try collecting it in a large white bucket to see if it has a green tinge to it. See our guide on "How to Clean a Green Swimming Pool (Algae)" for detailed instructions on clearing your algae. Make sure your chemicals are balanced before you shock and put algaecide in. And you may have to do this process a couple of times.


My pool is green and after treating with algacide, the water coming out in backwash mode is clear. What could the problem be.

User: Inyopools

Relabstract - Sounds like a damaged gasket. Check your spider gasket on your multiport valve. See our guide on "How to Replace a Spider Gasket on a Multiport Valve" for more information. Remember to shut off the pump every time you change the valve setting to prevent damaging the gasket.

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Tips & Warnings

Don't backwash excessively. Contaminates in the sand actually help the filter work more effectively - to a point. Monitor your pressure gauge for an 8-10 psi rise.

Never move the valve handle when the pump is on.

Don't vacuum your pool in backwash mode. You may clog the collection pipes (laterals) at the bottom of the filter.

Please Note:

Inyo Pool Products is not responsible for any injury or damaged equipment
while using our guides. Using our guides is doing so at your own risk.
These guides are suggested use of your pool or spa equipment and may vary
depending on which product you are using.