Please Critique Basement Bathroom Drain Rough Plumbing Plan

Discussion in 'Plumbing Code Questions' started by rcalliott, Feb 18, 2021.

  1. rcalliott

    rcalliott New Member

    Feb 18, 2021
    St. Louis, MO
    Looking for feedback on my planned drain rough ins before I start busting concrete to build a basement bathroom with a sink, toilet, tub/shower combo.


    Blue tape represents existing 4" PVC drain pipe under slab.

    PVC Fittings from left to right:
    • AAV (in the box) atop 2 inch tee serving the sink drain (will be recessed behind the drywall in the vanity).
    • Next is a 2" long sweep 90 degree turn from vertical to horizontal.
    • Then a 2" 45 degree fitting to get the pipe slotted into the 3x3x2x2 Double Wye.
    • Double Wye serves toilet above it via 3" pipe, and connects to 4x4x3 45 degree wye attached to existing 4" pipe 12" to 15" under the slab.
    • Fernco fittings with PVC stubs to attach wye to existing drain pipe, which flows from left to right in the picture.
    • From the right of the Double Wye is a 2" pipe with various 45 degree fittings to get the angle correct to the 2" p trap for the tub/shower combo (furthest item on the top-right).

    With a wet vent from the sink, my understanding of the toilet NOT being the last fixture on the pipe requires the Double Wye/Symmetric Fitting.

    Seems like some folks don't care for the AAV. on the other side of the top wall is my workshop with access to the main stack and a vent that goes up through the roof. If the AAV functions poorly in this configuration, I can tap into this 1.5" vent pipe...its just a pain I'd like to avoid.

    Any feedback and general comments/suggestions are appreciated.
  2. Sylvan

    Sylvan Still learning

    Sep 23, 2004
    plumbing - fire suppression - boiler inspector
    New York
    GET rid of the fernco coupling. Go with shielded couplings

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  4. rcalliott

    rcalliott New Member

    Feb 18, 2021
    St. Louis, MO
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