double sanitary tee vs double combination wye

Discussion in 'Toilet Forum discussions' started by Jfknz, Dec 22, 2012.

  1. Jfknz

    Jfknz New Member

    Due to a tight squeeze between the floor and ceiling below, we installed a double sanitary tee (accommodating a toilet on one side and a shower on the other). Upon receiving the documentation for the toilet (Toto model MS854114S(G)/MS853113S) we discovered that they recommend against this and instead suggest use of a double combination wye (see page 2 of Toto recommends wye in back-to-back toilet installations - which is not my situation as tee only serves one toilet and one shower.
    Has anyone had a problem (or success) using a double sanitary tee in a situation like mine?
  2. cacher_chick

    cacher_chick Test, Don't Guess!

    Land of Cheese
    The problem with doing it with back-to-back toilets is that the water from one toilet can shoot across and effect the opposite one. The shower drain does not flow as such, and should not be an issue.
  3. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    New England
    The velocity of the flushed water from the toilet is fairly fast...without the 'proper' fitting, it can shoot across to the other fixture (the shower). Probably not enough to come up in the shower, but it is a potential risk. It will also make snaking the line tougher as it may just go across rather than down.
  4. Terry

    Terry Administrator Staff Member

    Bothell, Washington
    It's going to mess with the shower. I would install a 3x2 wye lower down the stack for the shower and come up separately for the shower, and then revent at 42" above the floor.
    This is not a good plan what you have done.

    I would not put a shower opposite a toilet. Especially with the new ones that are using a 3" flush valve.
    Last edited: Dec 22, 2012
  5. hj

    hj Moderator & Master Plumber Staff Member

    Cave Creek, Arizona
    Depending on HOW you did the shower drain, NEITHER fitting may be "approved" or appropriate. The proper fitting would be a "back to back fixture fitting".
  6. Jfknz

    Jfknz New Member


    I just want to update this thread and thank those that replied -- esp. Terry for giving an amateur like me a forum to ask such questions.

    It's been 1.5 years since I started using the bathroom daily and at this point I'm happy to say cacher_chick's prediction is proving correct. I've had no problems with the 'unapproved' way I ran the toilet/shower drain. Having said that, I'd still be wearing doing it again given the very good point jadnashua made about problems snaking. I'd just like anyone stuck in a similar situation with so little space to work with to know that it worked - so far, so good.

    Thanks again, all.

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