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topic 29544

Washing machine drain line backs up

A discussion started in 2004 but continuing through 2017


Q. I have a washing machine drain line that over flows when the washing machine dumps its water, I have to stop the machine allow the water to drain off then allow machine to continue, On a full load I have to do it several times, I have paid to have a power auger clear the line but after a few weeks its backing up again, what can I use to clear the drain? Is Muriatic Acid [linked by editor to product info at Amazon] ok to use on a cast iron drain pipe? if so how much do I use.

Jeff S [last name deleted for privacy by Editor]
support service - Huntsville, Texas


A. Acid is not appropriate for metal drain lines. Lye type drain cleaners like Drano [linked by editor to product info at Amazon] or Liquid Plumber are more appropriate, although dangerous to people. This isn't a plumbing forum, but have you considered the possibility that roots have penetrated your drain piping? If so, new drain lines is the answer. Can you put a sock or stocking, or more formal filter in the discharge to capture the lint? Is it possible that you have created an air lock in the drain?

Ted Mooney, Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey


Q. My washing machine floods my floor with water when it is draining the tub water. The hose is in place in the drain pipe but the water fountains out the drain pipe. I have put a garden hose down the pipe drain, no water flows back. There is no blockage. What could the problem be?

Irene B [last name deleted for privacy by Editor]
- Oak Harbor, Washington

Plumbing for Dummies
from Abe Books



A. Well, seeing as I have the same problem myself, I guess I'm an "expert" :-)

I used duct tape to connect the drain hose to the drain pipe so the water can't escape -- see if that helps. Not the right answer, of course, will probably void your warranty, and maybe a code violation -- but it works for me on my decades-old Maytag.

Here's the real problem possibly: all drains require vents and your washing machine drain may not have one. Your bath, toilet, sinks, basins, all have vent pipes going up through the roof. When water needs to go down one of those drains, it just pushes the air that was in the pipe up the vent pipe. When you have no vent pipe, there's no place for the air to go to get out of the way of the water, so it has to "push back". Why doesn't the air just go down the drain pipe to get out of the way? Because air is much lighter than water, it keeps fighting to "float" back up the pipe. A plumber may have to install a vent. Good luck.

Ted Mooney,
Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey


Q. So how do we stop this air /water problem from happening?

Thank you STEPH ~

Stephanie Z [last name deleted for privacy by Editor]
- Selden, New York


A. Hi, Stephanie. You have your plumber put in a vent pipe, which is probably required by plumbing code anyway -- or you live with it, or you do unadvised duct taping things to minimize the leakage :-)

Ted Mooney,
Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey


Q. Like the person before, I too have a drain problem. The 2" drain line ties into a 3" drain line. The 3" line has a vent. It seems to my calculations that the backup is at the 2-3 inch joint. This is a 3x2 combo sanitary tee. The 3" line is clear (I know this because it is also a drain for another washing machine in the adjoining duplex.). What could be causing the back up?

James Crapitto
- Huntsville, Texas


Q. Our washing machine backs up, not into itself, not further down the line, but into the kitchen sinks! My wife has to stop the machine, wait for the water to gurgle down the sinks, and then restart the machine. This she does a few times until the washing cycle is done. The drainage system appears to be in a T-formation, with the kitchen drainage pipe continuing down toward the bathrooms, and the washing machine connecting about in between the kitchen and bathrooms to form the "T".
Would sincerely appreciate some help and advice.

Manuel S. Gonzalez
- Benbrook, Texas


Q. Having the same problem and I know I need a vent pipe on my washing machine. Where should it be placed to allow the air to escape?

Tracy Gordon
- Odenville, Alabama


A. You can see better drawings in a home handyman book, Tracy, but every plumbing fixture including a washing machine should have a trap and a vent. The trap keeps sewer gas out of the house. Good luck.

Ted Mooney,
Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey

Air Admittance Valve


A. Look into an Air Admittance Valve =>
This will let in air without have to run a vent up through your roof. Sure old timers will tell you this is "band-aid" plumbing but sometimes you can't vent up. Just remember the AAV will go bad at some point so make sure it is accessible. They are simple to add. Of course you should check to see if it is 'allowable' by the code in your area.

Chris Cook
- Parma, Ohio


A. I had the same problem but it turned out to be roots. Watch out for trees near your sewer line. They always are the main problem. I have worked for a Public Works Department for 30 years so you think I would have figured this one out :-)
But no, the trees were 50 ft away.

Richard Maag
- Edmonds, Washington

February 2009

Q. My washing machine drain is also overflowing. I have air vents to the from the main line 5 ft away. My old washing machine never overflowed. My newer Maytag does. I am told that it is the size of the drain line. My house built in 1975 has a 1.5 inch drain line from the washer. I am told that the newer washing machine force out water a lot faster than the older machines...and now need at least a 2 inch drain line to handle the newer flow rates. It sounds right. I wish there was a way to reduce the machine flow rate, since I must knock holes in my block wall to replace my old drain.

What solutions have the experts come up with?

bob pendleton
- Tempe, Arizona

Magic Vent

March 2009

A. Regarding washer machine drain problems. I just installed a Studor Mini-Vent today and am hoping this corrects the problem. I had to cut into the 2" line and install a tee in order to do this, but it was very easy.

If this doesn't correct the problem I am going to install a laundry tub and allow the washing machine to drain through it. This should slow down the water drainage and hopefully solve the back-up problems that we have been having as well. I have tried snaking the drain, about every type of drain cleaner and nothing worked. We also had an older washer and never had any problems until we had to replace it with a new one.

I will update this to let you all know if the mini vent works or not.

R Beavers
- Dallas, North Carolina

March 2009

Q. I've got this problem as well, after a mess up on my part (broke the drain stack off the main drain in the crawl space while trying to check it out). We've replaced the old 1.5" to 2" drain stack that was already there with a 2.5" stack and we're still having the problem though it's not as bad (with the old stack water would shoot out of the top of the stack like a fountain, now it kind of just bubbles). During the drain cycle on the washer I can stand at the pipe and if I hold the washer's drain JUST right and wiggle it a little I can get it to not overflow (though it comes close) once it does start to drain back down I can hear a distinct gurgling in the line -- is this indicative of a venting issue? I've got a feeling that it's just a vacuum issue (though our plumber did suggest getting the lines snaked).

David Senette
- Knoxville Tennessee

April 2009

A. Most of the drainage problems espoused here could be simply resolved by eliminating the usage of tub-type washers and employing front loaders. The latter use 1/3 the water of a top load machine, and using less of anything is a good thing these days. One-third in, one-third out.

Simple, but difficult and unreasonable if your top loader was a recent purchase. Replacing an older machine will pay for itself after several years -- less water, less water to heat, plus more gentle action on your clothing.

Rory B. Saillant
- Lake Worth, Florida

May 2009

Q. Our washing machine leaks intermittently. The repairman is stumped after coming out twice as there is no sign of a leak in the machine or where the outflow drains in the back wall. We think it may be occurring only after multiple back-to-back loads. Could water be backing up into the pan somehow from the pan drain? If it matters, this is an upstairs machine.

Brady Pregerson
hobbyist - Carlsbad, California

June 2009

Q. My name is Mary Jo and I have a similar issue with my machine. When I attempt to fill washer once it gets to certain height it starts running right back out drainage pipe of washer. In other words. my tub is not holding the water -- it's running right back out.

Mary Jo Davies
homemaker - Albion, New York

August 2009

A. When water comes right out of the washer as it's filling, it's a sure thing your hose is too low. this creates a siphon which pulls water down to the level of the outlet of the hose.

Solution: raise the hose. it should dump water at or a little above the level of water in the tub. measure from the start of the tub opening to the top of the washer, measure from the top of the washer to the floor, and subtract the smaller number from the larger. that's the height the hose outlet should be.

It will be higher on a top loader than a front-loader, unless you have an unusually high pedestal. washers have a small drainage pump that will make up the difference.

scott schrader
- mounds view, Minnesota

October 2009

Q. My washing machine used to drain the water completely.
I am using a Liliput washing machine. Suddenly, the drain stopped working.
There is a wire kind of thing given inside to pull it up so the water drains out.

When I pull this thread, its draining. Otherwise water is staying inside the tub itself.

I am not sure, if there is any blockade inside. How can I fix this issue?

Please suggest me.

Thanks, Sathish

Sathish Kumar
buyer - India

January 15, 2010

Q. I have been having the same exact problem with my washer! The "back-up" thing, that is. The house I just bought was built in 1947 and the new washer just backs up as soon as it drains. The pipe cannot handle the amount of water flowing out of the washer because it doesn't get enough air. They also didn't vent as many places as they do now. So, my vent is over the kitchen and the washer is about 6 feet away.
We have taken the pipe off, snaked, used a "water weenie" and ran 2 hoses full blast through it and it drains, when I try to use the washer, it comes out like a fountain. Luckily I have a window over the area and I quickly stuck the hose through it to finish my laundry.
There is this thing that my cousin has on her drain that seals it completely when the hose is in there and apparently they are commonly used in older homes. I am going to try that because the P-trap in in the wall and I don't want to rip it out yet until I re-drywall the garage. Has anyone else used one of these and do they work?

Denise Tucker
- Sacramento, California

April 1, 2010

Q. I also have the washer drain pipe that is backing up on the water discharge cycle. We have been in the house for 3 years, built around 8-9 years ago. Never had a problem befor, but after doing 5 loads one day it backed up on the 6th. It does drain once the washer is stopped, and the vent is right above the washer drain. I have snaked it as far as it would go, dumped drain cleaner, etc. without any change. Any suggestions? Thank you.

Don Pysz
- Imperial, Missouri

April 18, 2010

A. My washing machine has also been overflowing out of the drain tube. The wall rotted, I tore out all the rot, replace the 2 x 4's with pressure treat, and instead of using sheet rock in the laundry room I decided to use plastic bathroom board.

I have a 25' snake. I snaked the p-trap and came up clean. I went on the roof and snaked the vent as best I could - came up with mud looking stuff and hair.

I ran water hose full blast through the drain and through the vent and it did fine - however, the washing machine still backs up.

To reduce the flow rate I took the rubber drain hose off and stuck a metal washer in there - at the end where it connects to the washing machine - the metal washer is large enough so that it won't fall into the washing machine and won't get pushed through the drain hose. It fit perfectly and reduced the hose size about a third - and it was enough to fix the problem.

I sealed all the gaps at the drain / water supply box with Great Stuff expanding foam, and used caulking to seal all the base boards so next time it overflows it will stay on the tile floor rather than being able to sneak back in the wall.

Brian Elton
- Baton Rouge, Louisiana

April 19, 2010

Hi, Brian. Different installations have different problems, but to me it sounds like in your case you still have an air-lock despite the main vent. Picture this, although perhaps exaggerated:

drain line over a curb

If a pipe has any unvented high spot, air will collect in it. Think about what happens when water tries to flow in such a pipe: the only way water can go into the air locked area is by driving the air out. But how are you going to push that air -- that so desperately insists on floating -- down below the water at the other end of the air lock? You can't. If you have a situation anything like what is pictured, you have to fix the routing or have a vent at the high spot to let the air escape from the pipe. Good luck.


Ted Mooney,
Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey

April 27, 2010

A. I fixed the same issue for a neighbor

She bought a new washer that discharges water at a higher rate, causing her drain line to overflow. I cleared the line about 15 feet or so and no luck. I tried every way to fix it but just came to the simple, but not as neat, way of discharging the water into a plastic mop sink with a p-trap discharging into the drain line. This does the job and adds a mop sink in your garage and if you need to soak,clean etc you don't need to go to the kitchen. Do not discard chemicals or paints down the mop sink, not good for your cast iron or the ocean.

MOP SINK: $49 dollars plastic hardware: $15 dollars little bit of cutting and connecting handyman/plumber: one to two hours of labor. 25 to 80 per hour...all though you can do this yourself easy. ask your local hardware/home improvement personnel.

You might have to relocate the washing machine and dryer: extra hardware/material....not much but this will add to the labor per hour part. If they know what they are doing just two hours max

Rudy Repreza
- Orange, California

April 27, 2010

A. We bought a newer washing machine and our drain could not handle the flow, it would back up in the sink and overflow. We have 2" diameter drain pipes and vents. Finally solved the problem by renting a power snake, the one that works like a power drill. Threaded it as far as it would go, locked it and slowly went back and forth to clean the walls of the pipe. The drill motor rotates the snakes which beats against the pipe walls cleaning them. Slowly did this in one foot intervals. Locking the snake, pushing in and out, unlocking withdrawing a foot or so, relocking and pushing in and out with the drill motor rotating, until the hole drain was done. Takes some time and effort, but it did the trick, cleared drain and only cost $22 to rent the power snake. Note: Threaded the snake through just below the sink drain in our case. Good Luck.

Bob Clark
- Kent, Washington

June 2, 2010

A. I had this same problem and puzzled on it for six years. I tried everything: store-bought drain cleaners, home-remedy drain cleaners, plumbers, boiling water, everything. Then it finally dawned on me that the flow rate from the washer was more than the drain pipe could handle. I bought a washer drain hose that was narrower than the one on my machine. I clamped one into the other, effectively reducing the flow from about 1 1/2 inches (in diameter) to about one inch. This worked instantly and cost me about nine dollars.

Now I just need to replace all that rot caused by this problem. Wish me luck.

mike drago
- dallas, Texas, USA

July 1, 2010

A. House is 72 years old. It has copper pipe that goes into cast pipe. The 2 inch drain from the washing mashing connects somewhere under the kitchen sink. We figured this out by removing the kitchen sink clean out and running the washing machine. Water came out the kitchen sink drain clean out. We snaked it and the problem appears to be solved. Note. We had to remove the short extension on the kitchen sink drain clean out to get the snake to go down the pipe. We also flushed water down the pipe and watched debris go by at the septic side.

Hope this helps ...

John Bostrom
- Georgetown, Texas, USA

August 31, 2010

Q. We have a 30 year old home, that we've been in just over a year. We discovered that the washer discharge was backing up, I installed a venting device and I believe it helps on the discharge backing up, but we discovered accidentally that when we flush the toilet in the basement, the washer discharge pipe backs up, - but not all the time. We tried flushing it while the washer was discharging, and it backed up as well even after installing the vent.

The toilet discharges into a sump pump in the crawl space of the house, the sump pump discharge line joins into the washer discharge line under the house which goes to the main sewer line out the front of the house. The sump pump has a vent line that goes out to the back side of the house from the crawl space. The discharge line also has a vent pipe under the house to a small sewer vent in the crawl space as well.


Not sure what my next step is beyond asking for help here, possibly calling a plumber next, unless someone has another possible solution.

William Baggett
Homeowner / handyman - Atlanta, Georgia, USA

October 6, 2010

Q. Can you give me a solution of backup of foam only from washing machines drain? we bought a new whirlpool Cabrio washing machine and only foam backed up a few months later. Tried different cleaners and snake. Water drains okay. I do not think we put in too much liquid detergent. Our house was built 22 years ago. Never had foam problem with old washer. Thanks for any suggestion.

Junhai Zhang
homeowner - Parma, Ohio, USA

October 16, 2010

A. I have a problem with my washer drain water backing up into my double kitchen sink whenever the washer drains. I have been told to install an Air Admittance Valve, and I am not sure whether I should:
(1) install it under the kitchen sink
(2) I could simply connect to my washer drain pipe (with a sanitary "T" in the drain line, then connect a 90 degree elbow to this "T" and then attach the Air Admittance Valve to the top of the 90 elbow.

Any advise on this situation would be greatly appreciated.

F. Ross Kennedy
- Halifax, Nova Scotia, Canada

October 18, 2010

Hi, Ross. Although they call it an air admittance valve, I think they also let air get out of the line so the water can flow through it. As such, I think the ideal placement would at the high point of the line.^[See entry of Jan. 18, 2012]


Ted Mooney,
Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey

October 24, 2010

Q. Our Kenmore washing machine is draining the water but bubbles are backing up the drain. how do you stop this?

Joe Kraus
home owner - USA

October 25, 2010

Q. Hose that goes into washer drain, the water keeps coming back out when the washer drains the water. We have snaked it and put drain cleaner in it the snake seems to only go so far then stops?

Barb Nobile
homeowner - Gahanna, Ohio

December 1, 2010

A. GVii valve is a patented product that pressurizes the drain which keeps it clean and attaches directly to your washer hose. For more info go to my web site Thanks

Randy Jirasek
- Troy, Texas USA

December 1, 2010

Hi, Randy. Good to hear that you have a potential solution. But I'm not seeing in your posting or on your website an explanation about which of these problems it addresses or how. Since it is patented you should be free to explain exactly what it is and how it works so the readers can judge how likely it is to solve their problem. Thanks.


Ted Mooney,
Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey

December 1, 2010

The GVii is a valve that has a stainless steel check ball. When the washer is pumping out, ball comes up, which makes built-in air brake. It prevents hose popping out and overflow of drain pipe, and helps keep drains clean. Hope this helps! Thanks

Randy Jirasek
- Troy, Texas

December 9, 2010

Q. I have the same problem, and snaking the washer drain line does nothing. However, I have an air vent pipe that goes to the roof, which seems to be the issue. If I snake the vent pipe, the problem goes away for 2-3 weeks. Any thoughts on how to make this more permanent? Does the pipe go straight down to the drain, so I could pour drain cleaner down it? Thanks in advance for any solutions.

J McLaughlin
- Torrance, California USA

December 10, 2010

A. Our second floor washing machine began overflowing at the drain after a new pump was installed in the washer. Tried everything from snaking to the expensive camera down the line to find the issue. No problems, vent on roof was fine too. Augured down the line 75 feet to no effect.

What finally worked was installing a 45 degree piece of pipe to a y valve. The drain line now drops 2.5 feet to a trap, the trap comes up and the line goes about six inches across to the 45 degree piece then into the y valve where it connects to the vent pipe going up and also drops down into the wall of the house.

Jeff Stratton
- Ankney, Iowa, USA

January 19, 2011

A. The biggest issue with all of the above seems to me (or to be) that the volume of water used by older machines, is replaced by a larger volume of water used by the newer machines. Most of the pipes can handle the larger volume, but not at the same DISCHARGE as the newer machines. If you SEAL the gap from the machine to the drain line, eventually you have no air in the system.... eventually the water runs freely. While duct tape works, there must be a way to PLUG the drain hose into the line and seal it, solving all the problems.

Gabriel Holter
- gulfport, Mississippi, usa

Uniform Plumbing Code
from Abe Books


January 27, 2011

A. Most of the problems I have been reading here are due to improper plumbing connections and assemblies. The plumbing code specifically states that every trap has to be vented properly. Air admittance valves can work but do have the potential of failing. Location of the washer trap, height, length and height of trap arm and proximity of other plumbing fixtures, such as water closets and bathroom groups, can and do affect the performance of the washer drain. Only an experienced licensed plumber can identify if such plumbing drainage systems to be properly installed, either preexisting, altered or installed.

Steve Maldonado
- Georgetown, Texas, USA

Bacterial drain cleaner

February 12, 2011

A. Like most people I have also had this problem and found out that the soap we were using had a waxy type substance that was visible on the soap fill area. What worked was using a bacterial drain cleaner =>
which now I use a different soap and use the bacterial cleaner from time to time. Previous to this I put 170 degree water at full flow and the snake, the bacterial cleaner worked.

Brian Carlton
- Okanogan Washington

March 12, 2011

Q. I bought a washer a couple of years ago brand new, had to put it into storage, and now it isn't wanting to hold water, and it is all coming out the bottom.

michele quinn
student - cedar park, Texas USA

March 21, 2011

Q. I'm having this same issue. When the water goes to drain from the washing machine water spews out of the pipe behind the machine. Same machine I have had for 5 years and all of a sudden this happens. I can't figure it out...doesn't seem to be clogged. Please help someone ... I can't afford a plumber right now. Thanks in advance.

L Hall
- Houston, Texas, USA

May 15, 2011

Q. I have lived in my house for 15 years it was built in the 50's never had an issue now all of the sudden my washer,kitchen sink and bathroom sink are all backing up into my toilet. I do have a sump pump in my crawl space. We have rooted all the lines and rooted the vent on the roof. Nothing is seeming to help! I do have trees 2 in front 1 in back could it be roots?

Cindi K
- Lake Station, Indiana

May 16, 2011

A. Hi, Cindi.

You need a professional plumber to look at this. Sad to say it could be very bad. Many 1950s tract houses used the least expensive, and often unproven materials like drain pipes that were essentially cardboard steeped in tar.


Ted Mooney,
Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey

June 18, 2011

Q. I have the same problem,
October 16, 2010

I have a problem as Ross Kennedy's
"my washer drain water backing up into my double kitchen sink whenever the washer drains. I have been told to install an Air Admittance Valve..."

I am not familiar to this system.

Would you please let me know of the detail steps to fix this problem?


Woo-Young Yoon
- Pleasanton, California, USA

July 15, 2011

A. I had this problem in my house 30+ years ago. the house was built in 1935 and had 1 1/2" galvanized pipe for a drain for the washer. I reduced it to a 3/4" pipe which fit snugly into the washer drain hose. I also "T"ed off it and put in a directional valve with a clapper in it, so that air could get into the line but water could not get out. This allowed the washer to pressurize the line and force the water into the drain system. It was easy to do and worked for about 25 years at which time I replaced all the plumbing while remodeling the kitchen. what I found when I removed the old galvanized and cast drain lines was really ugly! I could not even see through them they were so corroded. I replaced the washer drain with 1 1/2" abs and it works great.
If you use too much soap it can also fill the drain line with too much bubbles and the water cannot get past it as it should.
New washers use less water than the old ones did, but drain faster due to higher spin speeds.
Another problem I have seen that slows drains is blocked roof vents, wasps or birds building nests in them.

Bob Petersen
- Orinda, California

August 20, 2011

A. I want to thank all of you for your suggestions. I made a list of the ideas that I wanted to try before calling a plumber. 1. Lye, gel type drain cleaner 2. Enzyme type drain care, build up remover. 3. Power drill plus snake. 4.restrict drain water flow from machine. 5. call a plumber 6. buy a new front loader machine.
We bought a new machine 3 years ago and had no problems until about 6 months ago. We just recently noticed that the drain was overflowing into the crawl space beneath the house. I checked the drain hose by running a cycle and having it drain into a trash bucket. I knew then the problem was in the plumbing. Luckily, I was able to clear the drain using 1, 2 & 3. It took me a week and cost about $45. Don't give up. The enzyme type drain cleaner took 3 applications. I ran boiling water thru after allowing the enzyme type drain cleaner to sit overnight. The last thing I did was to run the power drill auger through and that pulled up some hair. Good luck !

Frank Walsh
- Dunwoody, Georgia, USA

August 24, 2011

A. Our drain problem has been solved!! We are so happy. My husband inserted a 1" pvc pipe into our drain hose before the drain pipe. It diffuses the water, slowing down the amount of water into the line. We haven't had water on the floor, since.

Annette Pallowick
- Indian Harbour Beach, Florida, USA

September 7, 2011

thumbsdownThe same thing happened to my 2 year old machine. All of a sudden it is leaking water where the machine hose and pipe meet. My machine does not wring out water, GE said it is because of my pipe being not big enough. Why did the manufacturer never mention that there is a possibility to have this problem. They should have given us size of pipe drain not just us finding it out of the blue.

Erlinda A [last name deleted for privacy by Editor]
- Carson, California USA

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