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Washing machine drain line backs up


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 [affil link] 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 [affil link] 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, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - 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

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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, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - 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, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - 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, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

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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

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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, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - 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

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