How To Backwash a Pool Sand Filter

Written by:  Danny Rhodehamel
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 (3.75 OUT OF 5 STARS ON 10 RATINGS)

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

Video

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 140)

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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?

Thanks

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.

User: 

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.

User: Inyopools

Fuz - Because your pool equipment is above your pool's surface, the water in you pump and filter will tend to drop back into the pool through the suction lines. If your pool equipment is higher than normal, more water will flow back into the pool. You might consider putting in a check valve between the pump and pool to stop this back flow when you shut the pump is off. The initial bubbles coming out of the returns during priming is natural. My guess on the dirty water is it's coming from the filter. Sounds like your filter is draining too when you shut the pump off and when you turn it back on and refill the filter, the action may be dislodging some of the dirt in the filter - somewhat like a partial backwash only the dirt is going out the return ports rather than the waste line.

User: Relabstract

When I set back to Filter (after Backwash & Rinse), blows sand back in Pool??

User: Fuz

Hi inyopools, I have a sand filter (not sure what make but is has a plastic casing on top so you can see the water going through. The water seems clear to me but when I turn off the pump, the water seems to drain out over about 5 minutes. Then if I restart it after about an hour or more, it takes about 90 seconds to find its prime, and when it does a lot brown water come out of the return jets followed by some large air bubbles for a minute or so? Any ideas what is wrong as besides this the pool seems fine but I'm having to run the pump 24/7.

User: Inyopools

Ulysses - If you have low flow in all valve settings, it sounds like you have a blockage somewhere in your system. You already checked the pump impeller so that should be good. If you haven't changed your filter sand in 5-7 years, I would do that. Replace the top 6" of sand first to see if that makes a difference. Make sure some of your diverter valves are open - suction side and return side. Try snaking a line through your pipes to see if you have a line blockage. Please send me another comment, when you resolve this issue for feedback. Thanks

User: Ulysses

I do not know what the problem is: My pool pump has been working perfectly for the last couple of years. now, it has no suction to vacuum the pool. When i backwash, it spurs the water instead of what it usually did, water pumping steadily. the same occurs when i rinse.
i've already took the pump apart and found no debris around the propeller. the filters are clean. I do not know what to do

User: Inyopools

Bret - You may have a blown spider gasket in your multiport valve. See our guide on "How to Replace a Spider Gasket on a Multiport Valve" to see how to inspect and replace a spider gasket if required.

User: Bret

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?

User: Inyopools

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.

User: Inyopools

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".

User: 

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.

User: concerned

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

User: Inyopools

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.

User: nvr2l8

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!!!

User: Inyopools

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.

User: Rookie

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?

User: Inyopools

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.

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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.