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

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by molo, Aug 9, 2010.

  1. molo

    molo New Member

    Messages:
    840
    Location:
    cold new york
    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
  2. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    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??
  3. Jerome2877

    Jerome2877 In the Trades

    Messages:
    397
    Location:
    BC
    Maybe a backflow preventer on the second floor laundry and a blockage further down the line?
  4. molo

    molo New Member

    Messages:
    840
    Location:
    cold new york
    Thanks for the reply,
    The washing machine goes into an open drain and is not sealed.
  5. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,309
    Location:
    Cave Creek, Arizona
    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.
  6. kreemoweet

    kreemoweet New Member

    Messages:
    371
    Location:
    Seattle. WA
    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.
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