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Thread: Where to add washing machine standpipe to stack

  1. #1
    DIY Junior Member jerry_johnson's Avatar
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    Default Where to add washing machine standpipe to stack

    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:

    Name:  current setup.GIF
Views: 2752
Size:  5.2 KB

    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:

    Name:  modified 1.GIF
Views: 3463
Size:  5.6 KB

    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)

    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. #2
    DIY Senior Member dlarrivee's Avatar
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    Default

    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 by dlarrivee; 02-19-2012 at 01:29 PM.

  3. #3
    DIY Junior Member jerry_johnson's Avatar
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    Quote Originally Posted by dlarrivee View Post
    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.
    I should have seen that, here is the fix:

    Name:  modified 3.GIF
Views: 2022
Size:  5.6 KB

    Quote Originally Posted by dlarrivee View Post
    Also, you may run into issues with pipe diameter if those lines are in fact 1.5" right now.
    Do you mean code issues, or drainage issues, or both?

    Thanks,


    Jerry

  4. #4
    DIY Senior Member dlarrivee's Avatar
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    Both.

    Many codes require 2" for laundry these days.

  5. #5
    In the Trades Gary Swart's Avatar
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    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. #6
    Homeowner
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    If I designed washing machines I would allow the owner to select the pump speed by jumping a wire. Thats too smart tho....

  7. #7
    DIY Junior Member jerry_johnson's Avatar
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    Quote Originally Posted by Gary Swart View Post
    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.
    Yeah, that's what it sounds like,

    Thanks for the advice all.

  8. #8
    DIY Junior Member jerry_johnson's Avatar
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    Default 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:

    Name:  modified 3.gif
Views: 5106
Size:  11.6 KB

    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.

    Thanks,
    Jerry

  9. #9
    Moderator & Master Plumber hj's Avatar
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    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.
    Licensed residential and commercial plumber

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