2nd Floor Washing Machine Puts Water Into 3rd Floor Sink

Molo · Aug 9, 2010

Hello,
I am wondering what are the most common causes of something like this before I start to tear things apart to troubleshoot. When the second floor washing machine is running it forces water into the third floor sink drain into the sink.

Thanks,
Molo

Jimbo · Aug 9, 2010

Well, the only thing I can see that would cause that is that the drain the washing machine goes into is plugged, partially. The pump in the machine is strong enough to send water up to the third floor. I am surprised that it does not overflow the drain on the second floor........is the washing machine connected to an open fitting, or is it "sealed" into a pipe??

Sponsor · 2022-01-29T12:20:58-0800

Jerome2877 · Aug 9, 2010

Maybe a backflow preventer on the second floor laundry and a blockage further down the line?

Molo · Aug 10, 2010

Thanks for the reply,
The washing machine goes into an open drain and is not sealed.

hj · Aug 11, 2010

quote: The washing machine goes into an open drain and is not sealed.

Then it is IMPOSSIBLE for it to develop ANY pressure, much less what would be needed to force the water UP 10 feet or so to the third floor. Your analysis is faulty.

Kreemoweet · Aug 12, 2010

Pressure can very definitely be developed in drain pipes if the venting is not up to snuff. Probably the sink upstairs does not have adequate venting, so the trap contents are being
forced into the sink by the pressure from the washer drainage.

2nd Floor Washing Machine Puts Water Into 3rd Floor Sink

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