Washing machine plumbing problem

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by nickb7, Jul 20, 2010.

  1. nickb7

    nickb7 New Member

    Messages:
    7
    Location:
    Seattle
    I have a washing machine in my basement. The existing drain line is higher than the machine.

    The existing drain line is 2" ABS pipe mounted on the wall 5 feet above the floor and behind the washer. The drain line is a horizontal 2" line that connects to a 2" P-trap with 12" long vertcal riser. The flexible drain hose from the machine is hooked over the top the riser. 5 feet from the P-trap the horizontal 2" pipe connects to a vertical vent pipe that drops immediately (6"drop) into the 4" building sewer. The building sewer exists through the foundation wall and connects to the side sewer.

    The riser top overflowed recently, probably due to some lint build up, and this caused me to review the situation. It seems to me that the short riser is a weak point in my drain. It really can't be lengthened because the pump is already pumping up to a height of 6 feet. I was thinking of making a closed connection.

    What I was thinking of doing was sawing a few inches off the riser and fitting a wye piece. I would connect the flex hose to the branch using a nipple and clamp, and whatever reducers. To the top of the wye I was going to connect an air admitance valve. The valve is to break the suction if it ever gets into a syhpon back into the washer mode.

    Does this sound like it will work? Also I am a little worried about forcing the water out of the P-trap - do you think that could happen?
  2. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    Sounds like the trap is too high off the floor, and the riser is too short. 12" is way too short. Direct connection is a no-no.
  3. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,034
    Location:
    Cave Creek, Arizona
    The machine can pump higher, but if you direct connect it, the washer will fill with sewage and overflow if the main line ever is plugged. (It would still overflow the trap, but that is a bit more sanitary than having a polluted washer, and is a function of the lousy/poor way they provided for the washer discharge.)
  4. Terry

    Terry Administrator Staff Member

    Messages:
    15,294
    Location:
    Bothell, Washington
    Often times in that situation, they use a secondary pump that moves water to drain high up on the wall.


    That way when the washer drains out, it drains down to the lower tub with pump, and you don't have waste falling back into the washer.
    The pump would have a check valve and gate valve on it, so you can work on the pump if needed.

    Attached Files:

    Last edited: Jul 21, 2010
  5. nickb7

    nickb7 New Member

    Messages:
    7
    Location:
    Seattle
    Thanks for the helpful answers guys. Also thanks for the appropriate avatar.

    Jimbo: yes and yes. This is an existing condition and cannot be fixed unless I abandon the laundary and rebuild it upstairs. The plumbing in the existing basement laundary cannot be lowered without rebuilding the sewer main for a quarter of a mile.

    hj: yes the backflow is a concern. When you say "The machine can pump higher" are you thinking I should lengthen my riser to get more surcharge into the drain? i.e. add another foot of 2" onto the riser and hook the flex pipe on to that.

    terry: The sump pump is an option but is a lot of work. Why not just put the check valve on the washer hose? Also here is a question: when you connect the discharge line from the sump pump to the house plumbing do you use an open connection , like the washer hose hook, or do you use a closed connection?

    OK, do you think it would work if I installed a backflow preventor on the horizontal pipe downstream of the p-trap and put a lint filter on the riser?
  6. nickb7

    nickb7 New Member

    Messages:
    7
    Location:
    Seattle
    Oh and did I say thanks for taking the time and adding to your carpal to help me out. All your points are valid and much appreciated!
  7. Terry

    Terry Administrator Staff Member

    Messages:
    15,294
    Location:
    Bothell, Washington
    If you put the sump in, it would be hard piped higher up.

    A check in the washer outlet hose would seem to work, though I don't believe it's a code approved thing, opinions anyone?

    The avatar is fitting, I save that one for those that are putting down Seattle.
    The other day when I drove by it, I was wondering how long it will still be there. The city is getting closer and closer to the needle.
  8. nickb7

    nickb7 New Member

    Messages:
    7
    Location:
    Seattle
    I bet there is no such thing as a 2" backflow valve is there? And if there was it would just be another thing to go wrong.

    This started out as a way to increase the capactiy of my system so it wouldn't backup during washer dumping. Now I am concered about general back up from the sewer.

    When I was a little kid I liked to go snorkleing in the ocean. My parents bought me a plastic snorkel that had a 180 degree bend at the top of the breather tube. A ping-pong ball in a cage was attached to the underside of the tube end. If I submerged the snorked, the ball would float up and block the opening so that I did not suck in a lung-full of water. Something like this is what I need in the riser part of the system just below the hook of the washer hose. Anyone know anything similar?
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