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Thread: questionable rough-in diagram

  1. #1

    Default questionable rough-in diagram

    I posted this to the remodeling group today, since I AM remodeling, but I think it's more of a rough-in question and I didn't get any answers there. Sorry for the repost

    Quote Originally Posted by magicalpig
    Hi everyone. It's been a while since I studied up on rough plumbing, so I would appreciate some comments on this plan.

    I'm moving my kitchen sink to a position where it cannot be vented straight up. It will be under a window.

    The drain/vent from my upstairs shower passes by the proposed sink location at a horizontal distance of about 2 feet away.

    In the illustration you can see that the shower is the only fixture on this drain. However there is a wc and lav that might tie into its vent; I don't know.

    Is what I'm planning what's known as a wet vent? I'm quite sure that's not allowed here, especially since it spans 2 floors. Or does a wet vent refer to using another fixture's HORIZONTAL drain as your vent, while my picture shows the sink tapping into another fixture's VERTICAL drain?

    Well I'll try to stop wondering and questioning and await some more qualified answers. Thank you

  2. #2
    Forum Admin, Expert Plumber Terry's Avatar
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    Aug 2004
    Bothell, Washington
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    The picture above is not wet vented.

    Wet venting must be fixtures on the same floor and the pipe size is increased one size.

    Neither of these two things are happening here.

    The lower sink must have a vent run to the upper floor, where it can be revented above the shower or tub,

    Or it must have an AAV valve on the trap arm.
    Something like a Studor vent.

    I also do not see that the toilet is vented.

    Fixtures that "are" wet vented would look like the drawing below.

  3. #3


    Yes, I see what you mean. I think a new vent will be inevitable; and it shouldn't be that hard. I will run the drain straight down and tap into the drain stack below and then pull a new vent through the roof. I wont have to back vent with the upstairs bathroom as shown in my diagram since there is a covered patio with attic behind the sink on the first floor. It will require routing around the window but if I have 6" clearance above the sink flood level I should be okay, right?

  4. #4
    Moderator & Master Plumber hj's Avatar
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    Aug 2004
    Cave Creek, Arizona

    Default vent

    If the vent will exit the patio roof, make sure it is not near any windows for the second floor rooms.

  5. #5


    I'll be sure to read all relevant code on that, thanks.

    By the way, the kitchen sink, before I moved it, was already vented through this shower drain. It was just positioned on the other side of the drain! I hardly lived in the house 2 weeks before gutting the entire kitchen, so I never got to know any of the problems from this bad venting method.

    What I also find interesting is that I've had 2 plumbers come by to look at this sink situation, and although they each had different ideas and each at least acknowledged the existence of such a thing as "Code", neither one said I'd have to vent the sink through the roof, use an AAV, or tie-in to the shower's vent above all fixtures.
    Quote Originally Posted by hj
    If the vent will exit the patio roof, make sure it is not near any windows for the second floor rooms.


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