Proper Shower Drain & Vent Design?

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by jpb, Feb 23, 2006.

  1. jpb

    jpb New Member

    Feb 23, 2006
    Hi All,

    This is my first time here. I'm replacing a bathtub with a shower stall and I'm seeking advice on how to properly run, connect and vent a new 2" line.

    My first plan was to simply extend the 1.5" bathtub drain but quickly hit two issues: An existing 1.5" drain line and joist-notching. The first problem is surmountable by replacing the 1.5" line with a 2" line. The second problem, however, is insurmountable. To land the drain in the center of the shower stall, I need to move two joist bays over and this would require notching the top of two adjacent joists in violation of code (notches would occur mid-span and require too large a notch--the current notch where the bathtub drain tail lived is/was in violation).

    Although it might be easier to live with the current notch, locate the shower stall drain at the notch end, and replace the existing 1.5" line with a 2"--I've already purchased a shower tray with center drain and I'm committed to going forward with a center drain design.

    My new plan is to run the new 2" shower line parallel to the joist and to connect to the waste stack either via the water closet elbow (less work--see pic 2) or to connect directly to the waste stack farther down the line (more work). It would also be helpful to know (regardless of connection method) whether a new dedicated vent line is necessary or if the main 3" waste stack vent will suffice. (The distance from the proposed shower drain location to the main vent is ~8'. Please see pics:

    Thanks in advance for any advice / feedback. :)


  2. Terry

    Terry Administrator Staff Member

    Aug 17, 2004
    Bothell, Washington
    None of that would pass a plumbing inspection.

    Every fixture has it's own vent.
    You can't run a shower into the toilet arm.
    the shower should pull off the main line on it's own.

    Most places don't allow a sanitary cross for toilets, it should be a fixture cross.

    Vents on their back should be wye fittings, not san tees.
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  4. jpb

    jpb New Member

    Feb 23, 2006
    Terry, thanks for the feedback.

    So, if I understand what you're saying...the shower drain needs to be connected directly to the main waste stack and it also needs its own vent?

    BTW, When you say 'none of that would pass inspection', I presume you're referring to my proposal and not the existing piping. :eek: ;)
    Last edited: Feb 23, 2006
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