I live in a raised ranch. The toilet and shower are backed up to the laundry room. The sink and the washer use the same discharge pipe. When the washer drains, the water backflows into the sink and out onto the bathroom floor. The plumber has been here twice and installed a vent in the pipe but it still happens. About 7 years ago we installed the sink in this bathroom. We don't remember this over flowing problem until this new sink was put in. We don't know what changed with the new sink as we believe the height of pipes etc. remained the same.

All other water from upstairs kitchen and bathroom do not cause any problem. I assume they must leave the house through different piping than the one involved on the lower level. Also the shower and toilet on the lower level work fine - never any back wash anywhere.

What do we try next?

Did you ever snake the drain? It is once worked, it should work now. It is possible some construction junk got in it when the new sink was installed.

Yes, I've snaked it and never hit any obstruction as far as I was able to get it in. I know no debris fell in when the new sink was put in because I did it myself.

I was thinking that maybe I should call roto-rooter and have it done professionally. Someone suggested that I should put in a longer trap under the sink but I don't understand how that will help. What do you think?

I live in a raised ranch. The toilet and shower are backed up to the laundry room. The sink and the washer use the same discharge pipe. When the washer drains, the water backflows into the sink and out onto the bathroom floor. The plumber has been here twice and installed a vent in the pipe but it still happens. About 7 years ago we installed the sink in this bathroom. We don't remember this over flowing problem until this new sink was put in. We don't know what changed with the new sink as we believe the height of pipes etc. remained the same.

All other water from upstairs kitchen and bathroom do not cause any problem. I assume they must leave the house thru different piping than the one involved on the lower level. Also the shower and toilet on the lower level work fine - never any back wash anywhere.

What do we try next?


By your description you have placed the blockage in the washer/lavatory branch drain line. The washer is vented by the lavatory why was a extra vent installed? There's no doubt in my mind that the blockage is in the lavatory/washer branch. Are the drain pipes 1 1/2"? Snake from the lavatory vent and use a spade tip instead of a auger. Then flush the line out with boiling water to clear any grease, fiber and hair that's built up. I have trouble picturing your drainage layout. By rights the backup should flood the shower and not raise up over two feet to flood the lavatory. Is there something you're not telling us? regards, Tom PS, The "longer trap" idea brought a chuckle to these withered old chops.

Thanks for helping. The pipe is 1 1/2 inch pipe. The vent was put in by a plumber 3 years ago when this became a problem. I don't think the shower is hooked to this line at all because you never hear sounds from the shower floor drain when a wash discharges water. The plumber thought a vent was needed (I don't think there was a vent before this). The other weird thing is that I can go for weeks at a time where it doesn't overflow to the bathroom sink then all of a sudden it starts again. Before the vent was put in I did try the auger and boiling water and lots of drain cleaners but nothing made it better. When the plumber did the work he removed the wallboard behind the washer in the laundry room so you can see exactly where the washer drains out as well as where the sink pipe connects. The sink pipe connects about 12 inches higher than the washer pipe so this water is definitely going against gravity! The house is about 40 years old if that if that matters. Would a digital picture of the piping help?

Thanks for helping. The pipe is 1 1/2 inch pipe. The vent was put in by a plumber 3 years ago when this became a problem. I don't think the shower is hooked to this line at all because you never hear sounds from the shower floor drain when a wash discharges water. The plumber thought a vent was needed (I don't think there was a vent before this). The other weird thing is that I can go for weeks at a time where it doesn't overflow to the bathroom sink then all of a sudden it starts again. Before the vent was put in I did try the auger and boiling water and lots of drain cleaners but nothing made it better. When the plumber did the work he removed the wallboard behind the washer in the laundry room so you can see exactly where the washer drains out as well as where the sink pipe connects. The sink pipe connects about 12 inches higher than the washer pipe so this water is definitely going against gravity! The house is about 40 years old if that if that matters. Would a digital picture of the piping help?


Yes. Please send us a drawing of the drainage layout. Thanks, Tom

This is the best I can do (hopefully I created an attachment which is a photo of the pipes). The far left is the washer drain pipe; it is 46" from the floor and 34" to the horizontal pipe which is the approximate height of the sink drain. The white pipe is the new vent that is 18" high. To the far right behind the water heater pipe is the sink drain pipe. It is 32 " from the sink drain pipe to the washer drain pipe.

This is the best I can do (hopefully I created an attachment which is a photo of the pipes). The far left is the washer drain pipe; it is 46" from the floor and 34" to the horizontal pipe which is the approximate height of the sink drain. the white pipe is the new vent that is 18" high. To the far right behind the water heater pipe is the sink drain pipe. It is 32 " from the sink drain pipe to the washer drain pipe.


The pictures didn't come through. Your "new vent" is only 18" high? Is that where it revents back or is that the terminal height in the wall? How high is the washer standpipe from the trap? Your blockage is located downstream from the lavatory and should be able to be reached through the lavatory or the washer vent. Try doing the picture thing again. Regards, tom

This site restricts the size of attachments permitted so there was no way I could upload it. I tried as gif, doc, bmp and jpeg - all too large. I tried as black and white photo and still too big for what is permitted. Is there a way I can send you an email with the photo as attachment?

This site restricts the size of attachments permitted so there was no way I could upload it. I tried as gif, doc, bmp and jpeg - all too large. I tried as black and white photo and still too big for what is permitted. Is there a way I can send you an email with the photo as attachment?


Send the pictures to, [email protected] and head the E-Mail up PLUMBING so it will not get overlooked. Thanks, Tom

This is the best I can do (hopefully I created an attachment which is a photo of the pipes). The far left is the washer drain pipe; it is 46" from the floor and 34" to the horizontal pipe which is the approximate height of the sink drain. the white pipe is the new vent that is 18" high. To the far right behind the water heater pipe is the sink drain pipe. It is 32 " from the sink drain pipe to the washer drain pipe.


OK Al,

I have the pictures, (great shot of your thumb). WOW! Where do you live and hold old is your house?
I haven't seen copper drainage for years. The only place that the problem could possibly be is in the 2" washer drain. If I were going to snake out the line I would pull the vent and go in through the tee.
Now let's talk about the vent the plumber installed. Nice job, wrong place! It doesn't vent a thing. Let me explain. Section 703.5(b) of the Standard Plumbing code under the heading, Prohibited Traps states; "Full "S" traps are prohibited. I can see two full "S" traps in your pictures. To be effective and legal the vent must be installed ahead of the trap. ( The trap coming off the branch of a tee and the vent coming off the top) Your plumber install the mechanical vent downstream from both traps consequently it's not venting anything. But hey! The upside is that while it's not doing any good, it's not doing any harm. Your "S" traps are probably grandfathered in and have been operating for years. I just wanted to call your attention to it and the fact that you are unvented on both fixtures. Snake from where I told you to and my bet is that will solve your problem. Regards, Tom


Perhaps when your house was plumbed "S" traps were legal but they have been outlawed for years

Try uploading in TIFF

Hello Royalfuzziness,

Welcome to the plumbing website, you responded to a 6 years old post, always check the date of the post on the top left corner before responding to thread, Thanks.

John