Where to add washing machine standpipe to stack

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by jerry_johnson, Feb 19, 2012.

  1. jerry_johnson

    jerry_johnson New Member

    Messages:
    4
    Location:
    Big Lake, MN
    Hi,

    I have a question about everyone's *favorite* topic, adding a standpipe for a washer drain.;)

    Right now, I just have the washing machine draining into the sink, and I'd like to have a cleaner look with the standpipe.

    Here is a schematic of the setup right now:

    current setup.GIF

    All the DWV lines are black 1 1/2 inch ABS.
    Now, I guess the first question--is the current setup considered correct?
    I know these should probably be 2 inch lines, but all this was done, I assume, when the house was built, in 1990.

    What i am thinking of doing is this:

    modified 1.GIF

    Tie the standpipe into the line that goes to the wye, so that the standpipe will drain below the laundry tub, and venting off that same line.
    San tees for all new connections as needed, put the standpipe at the correct height. Still use 1 1/2 inch ABS (don't think I can tie 2 inch into 1 1/2 inch, right?).
    I would tap the standpipe vent close to the current stack, to avoid running lines over the laundry tub--all this is in an exposed area of the basement, and i don't want extra lines running over the laundry tub, if I can avoid it.
    Both the drains would be at about 18 inches off the floor--in the diagram, it looks like I have the standpipe line higher, but that was just for purposes of the sketch. (Also, the washer is in front of the standpipe:D)

    Is what I have in the second diagram correct? Should I tie into the other line instead, or do I need to find another line altogether?
    Let me know if I am way off base, or if there's any other way to do it.

    I am not offended with any advice given, just want to make sure I do stuff right.

    Thanks,

    Jerry
  2. dlarrivee

    dlarrivee New Member

    Messages:
    1,172
    Location:
    Canada
    You're a little off with your vent for the stand pipe.

    The line you want to to into for the vent is the one WITHOUT any fixtures draining into it, a DRAIN is NOT a VENT.

    Now it just depends on the fittings you use to make those new connections.

    Also, you may run into issues with pipe diameter if those lines are in fact 1.5" right now.
    Last edited: Feb 19, 2012
  3. jerry_johnson

    jerry_johnson New Member

    Messages:
    4
    Location:
    Big Lake, MN
    I should have seen that, here is the fix:

    modified 3.GIF

    Do you mean code issues, or drainage issues, or both?

    Thanks,


    Jerry
  4. dlarrivee

    dlarrivee New Member

    Messages:
    1,172
    Location:
    Canada
    Both.

    Many codes require 2" for laundry these days.
  5. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,350
    Location:
    Yakima WA
    You might be better off to stay with what you have. Your drain lines are too small and you may get backup. Right now, the laundry sink acts as a buffer.
  6. Hackney plumbing

    Hackney plumbing Homeowner

    Messages:
    1,174
    Location:
    Alabama
    If I designed washing machines I would allow the owner to select the pump speed by jumping a wire. Thats too smart tho....
  7. jerry_johnson

    jerry_johnson New Member

    Messages:
    4
    Location:
    Big Lake, MN
    Yeah, that's what it sounds like,

    Thanks for the advice all.
  8. jerry_johnson

    jerry_johnson New Member

    Messages:
    4
    Location:
    Big Lake, MN
    One more bright idea

    So, I want to put one more idea out there before i give up on this altogether:

    (May be a dumb question.)
    Is a vent required to tap into the same pipe the waste drains into?
    What I mean by that, is would something like this work:

    modified 3.gif

    I'd like to know if I can run the washer drain as a 2 inch pipe, draining into a 3 inch pipe, venting off the same 1 1/2 inch vent I planned in my above diagram.
    I thought I read somewhere you can use 1.5 inch to vent 2 inch, but correct me if I'm wrong.

    The distance from the planned standpipe trap to the vent is about 3 feet, then a run of about 5 feet to get to the 3 inch pipe.
    The 3 inch pipe has one WC, one bathtub/shower, one vanity above the proposed washer entry, and one vanity below.

    I think that's all I've got. Really wish the previous owners would have used 2 inch for the laundry lines.:p

    Thanks,
    Jerry
  9. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,642
    Location:
    Cave Creek, Arizona
    Once you install the vent at the proper location, it makes little difference how far you have to run the rest of the pipe. On the surface, what you show will work. Unless the previous owners did their own plumbing, it was the "plumber" who installed the 1 1/2" drain lines, probably because it was cheaper.
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