tub shower combo drain/vent question

Discussion in 'Shower & Bathtub Forum & Blog' started by rainy island, Sep 7, 2013.

  1. rainy island

    rainy island New Member

    Sep 3, 2013
    Victoria BC
    Hi there,

    I'm contemplating options for a bathroom renovation and was hoping to get some advice about drain/venting requirements for one of the potential scenarios. While a significant chunk of the job will be DIY, I plan to contract with a licensed plumber for the actual drain/venting work.....not an area where I possess the necessary confidence/competence. I thought I'd seek some advice here first, simply so that my wife and I can narrow down our options.

    The current bathroom is an en-suite in a bungalow. Drain, water, hydronic heating are all easily accessed from the 4 foot crawl underneath and happily, the people who built the house in 1976 met or surpassed the code of the day.....as I've discovered doing other reno's, they took no shortcuts with electrical, heating or plumbing.

    The current bathroom has a shower-in-tub unit, WC and single lav. We are thinking about moving a non-bearing wall and stealing three feet from the bedroom to expand the bathroom so that we could install a separate tub and shower. One option is to install a linear combo tub/shower unit (the type where the tub and shower pan are side by side in an integrated 8 foot acrylic unit).

    The question is whether the two drains off the unit (which are 27 inches apart) could share the same 1 1/2 inch trap and drain and 2 inch vent, or whether they need independent traps?

    I believe I (or more accurately the plumber) still needs to extend the waste line by three feet, move the waste stack and the shared 2 inch vent (which currently vents the tub/shower and WC) at the top of the waste stack into the new wall, but sharing a trap would require one less drain line connection at the stack.

    From a code perspective, I'm in Victoria BC, and for the record, it is raining.


  2. Terry

    Terry Administrator Staff Member

    Aug 17, 2004
    Bothell, Washington
    Code doesn't allow putting those two fixtures into one trap.

    I saw a similar remodel where the handyman had done that. When the tub drained, black goo came up in the shower pan.

    The walls will be out for this remodel. Figure out a way to install a vented trap for each fixture. You could get by with a double fixture fitting perhaps and use one vent, but it's not a big deal to come up with two vents and revent higher up either.
    ABS or PVC pipe and fittings hardly cost anything.
    Last edited: Sep 7, 2013
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  4. rainy island

    rainy island New Member

    Sep 3, 2013
    Victoria BC
    Thanks for the quick reply Terry. I agree that the additional cost is minimal. Not surprisingly, your advice makes a whole lot of sense.

    Thanks again

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