Please Review Our Plan for Kitchen/Half-Bath Rough-In

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by westminster, Nov 13, 2009.

  1. westminster

    westminster New Member

    Aug 20, 2009
    Hi. We are renovating our kitchen and adding an adjacent half-bath. This is our very first plumbing project, and we wanted to run our DWV rough-in by you experts to get your input. Here is a drawing of our current plan:

    The picture shows the back wall of our house, which is where the kitchen sink and d/w will be, centered under the window. We are framing a new wall perpendicular to the back wall to carve-out a half-bath on the left side of the drawing. The toilet will be on the exterior wall and the lavatory will be on the new perpendicular wall. We are tieing into the existing 3" cast iron stack in our basement which connects under a slab to the main drain. The basement is full-height and unfinished. We are also tieing into a 2" galvanized vent to the roof which projects down to the kitchen ceiling from the second floor. All of the walls and ceiling are open right now so that's not an issue.

    We are in NYC and under a modified version of the IPC (, although this won't be inspected.

    In the current plan, the 3" branch drain is running along the back wall of the basement about half-way between the floor and ceiling, so as to preserve access to the basement window (although this is not essential). The floor joists for the kitchen do run parallel to the back wall and are 2x10, so it may be possible to run the drain in the joist cavity instead. But we thought it might be difficult for us to work with limited space.

    You will notice there are some minor set-offs in the stack vent, in the kitchen floor and ceiling. This is to get around our foundation wall, which is a foot thick, and also to meet up with the vent in the kitchen ceiling, which comes down from the second floor at a difficult angle. The branch vent will run in a joist cavity in the ceiling of the kitchen, since we are not planning to drop the kitchen ceiling. We will, however, drop the bathroom ceiling, which is why we planned to have the kitchen sink and lavatory vents turn out of the stud bays at 90 degrees and into the half-bath ceiling before running horizontal.

    I'm not sure if this is clear from the drawing, but the drain for both the lavatory and kitchen sink are running up through the new wall (2x4) that will separate the kitchen from the half-bath. The trap arm from the kitchen sink would then run outside the finish wall (parallel to the back wall, through a cabinet) to reach the sink. We set it up this way because of the fact that the sink will be under a window that is very wide (4 feet) and low (just an inch or two higher than our countertop), so I think that we would have to run the vent horizontal below the sink flood rim (against code) if we were to try and bring the kitchen sink drain up from behind the sink. In addition, we would have to drill holes through two studs in an exterior wall (one load-bearing, and one cripple), which we were hoping not to have to do, since we were planning to use 2" pipe. We could also bring the kitchen drain up in the stud bay to the right of the window, which would avoid having to run the vent pipe horizontal, but we would still have to drill through the load-bearing stud. Note that the studs are 100 years old and close to a true 2" x 4". Code would also allow us to use 1.5" on the sink drain, although we thought it was better to oversize. Maybe there is a better way to do this. We would be very interested to hear what you would do if you were in our shoes.

    As for the bathroom, our main question is whether we are okay with wet venting the toilet as shown in the drawing. Our code does seem to allow this based on the way that I've set it up. Since the wet vent would need to be 2", we were planning to run it along the basement ceiling since the pipe is too big to run through the studs and we didn't want to drill holes in our joists. While I don't want to have to run unnecessary pipe (we already have our hands full), I do want to make sure that we end up with a really well-functioning toilet, so I'm not sure if it's better to go ahead and run an individual vent for the toilet. In particular, I am wondering if the length of the wet vent makes a difference here -- it will probably end up being around 6-7' from the toilet flange to the sanitary tee on the lavatory.

    We're very interested to hear any and all thoughts on our plan, as we are completely new to this and want to make sure we don't make any major mistakes before we glue everything up and wall it in. Thanks in advance -- we completely appreciate your taking the time to share your advice and expertise!
  2. westminster

    westminster New Member

    Aug 20, 2009
    Sorry, duh: wherever I said TY, I meant to say combo...

    Last edited by a moderator: Jan 12, 2010
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  4. shacko

    shacko Master Plumber-Gas Fitter

    Jan 22, 2006
    Master Plumber-Gas Fitter
    Rosedale, Md
    1: The wye you have to wet vent the toilet I would move to the same plane as the toilet arm and then run your lav.

    2: The vent off the kitchen can be 1 1/2in.

    3: Where you have the kitchen and the lav. vents tied together you can't use a tee, you will have to use a 2x1 1/2in. wye, 2in. ell and a 1 1/2 45 or street 45.

    The rest looks fine to me, but somebody else may see something I missed. :)
  5. westminster

    westminster New Member

    Aug 20, 2009
    Cool, thanks.

    Sorry if this is a stupid question, but could you walk me through how to tie-in the kitchen and lav vents with those fittings? I'm having trouble visualizing it...
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