Drain & Vent questions for new tub/shower

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by cwilson, Sep 14, 2006.

  1. cwilson

    cwilson New Member

    Messages:
    4
    Location:
    Florida
    Hi,

    I'm working on a bathroom remodeling project that will involve relocating a walk-in shower and adding a separate 6' tub. To do this we are expanding the bathroom to also use the floor space from the adjacent walk-in closet.

    The existing floorplan is shown in the attached pic "current_layout.gif", and the planned changes are shown in "new_layout.gif".

    A few things to note on the existing floorplan:
    • This bathroom is on the second floor of the house
    • The existing DWV lines are shown in red color
    • The existing shower has a 2" drain
    • The main stack is 4", and the exterior wall in which it resides is studded with 2x6's. The other exterior wall (top of the picture) is 2x4 studded.
    • All of the existing fixtures in this bathroom vent through the main stack
    I have a few questions on the drain and vent layout for the tub and shower in the new layout:
    1. Can the shower and tub share the same 2" drain (each with their own trap, of course)? (Note, this is shown in a green color in the new_layout.gif picture)
    2. What is the best way to vent the shower and tub?
    3. Any other potential gotchas to worry about?
    Thanks for your help!

    Best,

    Chris

    Attached Files:

  2. Terry

    Terry Administrator Staff Member

    Messages:
    15,418
    Location:
    Bothell, Washington
    The shower and tub can share a 2" waste line, each must have their own vented p-trap.
    The vents prevent the traps from siphoning.
    Most places allow five feet between a trap and a vent on 2" pipe.
  3. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,263
    Location:
    Cave Creek, Arizona
    piping

    The tub and shower can share a vent, but not the way you show it. In fact the pipe to the tub is already too far from the vent under most codes.
  4. Terry

    Terry Administrator Staff Member

    Messages:
    15,418
    Location:
    Bothell, Washington
    hj is right, if you have a fixture cross between the fixtures, you can share that vent.

    It's doubtful that on a second story the way you have it drawn, that a fixture cross would fit there.
  5. cwilson

    cwilson New Member

    Messages:
    4
    Location:
    Florida
    Hi Terry/HJ,

    Thanks for the replies. Running separate vents isn't a problem, but I'm struggling with how to route them. Since the top wall in the picture is a 2x4 exterior wall, a 1-1/2 - 2" vent pipe can't go in there (please correct me if I'm wrong).

    I could vent the shower through its South wall (assume North is the top of the picture), but that would mean I have to run the vent horizontally (with 2% slope) for 3-4' until I get to that wall. Would that be ok?

    For the tub, I'm not really sure what to do, unless it could share the vent I described above for the shower.

    The floor is supported by trusses, so there is a lot of open space to route things however they need to go. However the vents are routed, I would end up tying them back to the main stack in the attic.

    Again, thanks for the advice.

    Best,

    Chris
  6. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,263
    Location:
    Cave Creek, Arizona
    vent

    The actual site will determine how you do it, but if it were I, I would try to get the vent in the dividing wall between the tub and shower and then branch out to the tub and shower from there. The actual way of doing so would depend entirely on the physical space available to do it, and possibly some cleverness in installing the fittings.
  7. cwilson

    cwilson New Member

    Messages:
    4
    Location:
    Florida
    Hi HJ,

    Thanks for the follow-up. So if I understand you correctly, I would have the following scenario:
    1. drain from shower would go to the main 4" stack on the East wall
    2. drain from tub would wye into the shower's drain line
    3. vent would be taken vertically off the shower's drain line inside the half-wall between the tub and shower
    4. once above the flood line for the shower and tub, vent could go horizontal to get around the glass panel in the shower on top of the half-wall between the tub and shower
    Does that sound about right?

    Seems like I'll still need to figure out a way to get the vent up the northern exterior wall and into the attic, but I may be able to cut back into the bathroom with it before hitting the top plate (so as not to compromise the wall's structural integrity).

    Again, thanks for your help.

    Best,

    Chris
  8. cwilson

    cwilson New Member

    Messages:
    4
    Location:
    Florida
    wet vent possible?

    Following up on my last post to this thread, I'd just like to confirm:

    Is it ok to "wet vent" the tub the 3' or so up the shower's drain line to the half-wall between the tub and shower and take a single vent off vertically at that point? This vent (a re-vent, if I have my terminology correct) would then rise vertically to at least 6" above the flood line of the tub and make its way into the attic to ultimately reconnect with the main vent stack on the East wall in the picture.

    In considering the drainage requirements and wet vent capability, please note the shower will have two separate shower heads (one at each end) as well as 4 body sprays.

    If the wet vent is not ok, what approach is generally taken to get a vent line vertically 6" above the flood line of a garden tub like this before going horizontal, since the tub's overflow is less than 6" from the top of the tub surround?

    Again, thanks for your help.

    Best,

    Chris
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