1. hello_mundo

    hello_mundo New Member

    Messages:
    4
    Location:
    Santa Cruz, CA
    I'm rough plumbing a house I'm building and I've gotten stuck on this one wall where two bathrooms meet back to back.

    I'm worried about where the shower and tub wastes meet at that double-fixture tee. Is that okay? Is that an okay way to vent those two fixtures? Is this long main waste line vented properly?

    The toilets are wall-hung in Geberit carriers and that's why the drain is in the wall with the vent following behind it.

    [​IMG]

    Thanks for your time!
  2. Terry

    Terry Administrator Staff Member

    Messages:
    15,050
    Location:
    Bothell, Washington
    For the toilets you would wye or combo off the main line and vent between that fitting and the fixture.

    The way it's drawn now is wrong.

    The lavs and the tub/shower combo is right.
  3. hello_mundo

    hello_mundo New Member

    Messages:
    4
    Location:
    Santa Cruz, CA
    Thanks Terry. I was looking at the Geberit Install documentation and they had the vent set up the way I've drawn it. But I think I understand why your way is better. Thanks!
  4. Terry

    Terry Administrator Staff Member

    Messages:
    15,050
    Location:
    Bothell, Washington
    I imagine they have the vent downstream, and that is how you vent.
    But when you add other fixtures before the vent, it is no longer downstream.
  5. jar546

    jar546 In the Trades

    Messages:
    432
    Location:
    USA
    Don't worry about the double tee for the Tub and Shower. That is not a problem at all. Only be careful when you double tee back to back toilets. In that case, you need to have at lease 18" of horizontal pipeon each side before it hits the tee from both sides.

    Don't forget all of your vertical to horizontal connections must be Wyes and not tees on their back (except for vents).

    I agree with Terry's assessment
  6. hello_mundo

    hello_mundo New Member

    Messages:
    4
    Location:
    Santa Cruz, CA
    Thanks guys! I really appreciate your time and help. This forum rocks!
  7. nhmaster

    nhmaster Master Plumber

    Messages:
    3,189
    Location:
    S. Maine
    The only problem I have with back to back san tees is when it comes time to run a snake down the drain it usually scoots across to the other fixture.
  8. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,689
    Location:
    Cave Creek, Arizona
    Really?

    quote; Only be careful when you double tee back to back toilets. In that case, you need to have at lease 18" of horizontal pipeon each side before it hits the tee from both sides.

    1. WE cannot use a double tee/cross for back to back fixtures of ANY kind.
    2. 18'' of horizontal pipe each way, plus a "cross", would give you at least an 18" toilet roughin on both sides more if you are not counting the elbow.
  9. SewerRatz

    SewerRatz Illinois Licensed Plumber

    Messages:
    1,705
    Location:
    Chicago, IL
    Thats why You put a wye combo on the vent and run the pipe to the nearest wall with a plug so you have a clean out on the drop.
  10. theplumber

    theplumber Member

    Messages:
    49
    Location:
    CA
    The only issue I have is the sizing of the wasteline for the w/c's. I could have sworn you could only keep to 3" if the toilets were at least 16' apart. Otherwise you have to go to 4" after the drop from the toilet closest to the sewer if they are closer than that.

    It may depend on local codes, I'm not sure if that's just an L.A. thing or if I'm completely mistaken.
  11. jar546

    jar546 In the Trades

    Messages:
    432
    Location:
    USA
    Exception: Back-to-back water closet connections to double
    sanitary tees shall be permitted where the horizontal
    developed length between the outlet of the water closet and
    the connection to the double sanitary tee pattern is 18 inches
    (457 mm) or greater.

    I don't agree with it but it is allowed.
  12. hello_mundo

    hello_mundo New Member

    Messages:
    4
    Location:
    Santa Cruz, CA
    Quote: I could have sworn you could only keep to 3" if the toilets were at least 16' apart.

    I'm not positive, but I designed it this way because the code book said that 3" ABS could support 20 fixture units (that's IRC... UPC says 35) on a horizontal branch. A W.C. is 3 fixture units, so that allows lots of room.
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