Drain/Vent layout Question

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by john330, Jan 3, 2009.

  1. john330

    john330 New Member

    Messages:
    3
    I am adding an upstairs bathroom and have some questions about how I can vent the system.

    The flow of the drainage is sink->shower->toilet. The sink drains into 1.5" pipe which then changes into a 2" pipe before the shower trap. The shower drains into the 2" pipe which then changes to a 3" pipe before the toilet drains into the 3". The drain then continues to flow down to the crawlspace and then on to the septic tank.

    My questions are 1) Will this drain layout work? and 2) How can I vent the shower and toilet together? (The sink will be vented by itself to the attic and tied into the shower/toilet vent before exiting the roof).

    Please note - in all pictures, the sink and it's drain are not shown, but are upstream of the shower.

    Can I vent the shower/toilet after the toilet as in "Figure 1"
    or
    Should I vent the shower and wet vent the toilet to the shower vent as in "Figure 2"?
    or
    Should I vent the toilet and tie in the sink/shower drain downstream of the toilet vent as in Figure 3?

    Attached Files:

  2. SewerRatz

    SewerRatz Illinois Licensed Plumber

    Messages:
    1,705
    Location:
    Chicago, IL
    Why don't you combine figure 2 and three? If you have room to put a vent by the shower and room to put it by the water closet all is good. You can tie the vent near the shower into the vent on the other side of the water closet inches above the drain.
  3. john330

    john330 New Member

    Messages:
    3
    Thanks SewerRatz.....venting both is an option, I was just seeing if there was an easier/simpler way.

    You mention combining figures 2 and 3, but can I combine 1 and 2 instead? Is there any reason why the sink/shower drain can't be upstream of the toilet or does it need to tie in to the 3" pipe downstream of the toilet?

    Thanks again!
  4. SewerRatz

    SewerRatz Illinois Licensed Plumber

    Messages:
    1,705
    Location:
    Chicago, IL
    Yep can combine 1 and 2 just fine. After I posted I thought about what I said and was thinking have the shower at the end will help wash down the line better.
  5. jar546

    jar546 In the Trades

    Messages:
    432
    Location:
    USA
    Personally I would just do #2 but increase the vent to 2-1/2" since you will be pulling at least 5 dfu's. Save yourself work, pipe and expense with the same result.
  6. jar546

    jar546 In the Trades

    Messages:
    432
    Location:
    USA
    I would set up the shower with a 2" pipe and trap size then at the beginning of the 3" horizontal line Tee up to your 2-1/2" vent for the water closet.

    Your 2" trap for the shower can be 8' away from the vent at a 1/4" per ft slope but it sounds like this will be relatively close so vent to trap distance does not sound like an issue for you.

    Is there a bathroom sink?

    Good luck.
  7. john330

    john330 New Member

    Messages:
    3

    There is a sink on the other side of the bathroom that will be vented by itself and tie into the shower/toilet vent in the attic before exiting the roof. Below is an overhead picture of the layout.

    The black is the drain and the red dots are where I can vent up. I can't vent through the "Back Wall" without add'l framing because it partially sits on a floor joist.

    Thanks for the advice........

    Attached Files:

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