New Bathroom Plumbing Rough In Help

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by HiQ, Jan 4, 2021.

  1. HiQ

    HiQ Member

    Joined:
    Jan 4, 2017
    Location:
    Manitoba
    Hey everyone. I've done some personal DIY plumbing here and there, mainly finish stuff or modifying existing. My BIL wants to add a bathroom to the house he purchased and has enlisted me to help. He's handling all the framing and boarding/mud/tape/etc, but I am up for the wiring and plumbing. Wiring is no issue, but I keep flip flopping on the best way to plumb this thing.

    It's going to be a fairly easy layout. Lav, WC, Tub all on one 2x6 wall. We can install a new vent wherever through the roof. Joists run parallel to this wall so we can keep the 3" pipe nice and tidy up in the joist space (hopefully). The run isn't too long before we need to turn and follow the bulkhead so we should be good on slope.

    Bathroom.jpg

    I attached a picture I found online, but it looks like the gold standard for plumbing. Everything is individually dry vented and honestly seems a little overkill. The differences with my BIL's layout are its going to exit to the right of the tub (this picture it's on the left) and his will run parallel to the joists (this runs below the joists which are perpendicular). Flipping the bottom of the picture is easy enough, but the biggest issue is the space required to vent the WC.

    Oh as for dimensions, it's going to be fairly small. 2x6 wall consists of 30" for vanity, 30" for WC and 36" for tub all side by side (8'x5' bathroom).

    Should I be looking at just dry venting the lav and then using it as a wet vent for the WC? I assume I'd need a 2" vent in that case? Or do I just wye in another dry vent after the WC? Can I eliminate 1 or 2 of the vents in this layout to ease installation? Any other suggestions? We're in Canada if that matters, but I don't think this will end up being inspected anyways (still want it done right though).

    Thanks!
     
  2. Jeff H Young

    Jeff H Young In the Trades

    Joined:
    Feb 27, 2020
    Location:
    92346
    starting at tub 3x2 combi looking up for a 2 x1 1/2 x1 1/2 santee then a 3 inch wye with a closet bend on the branch continue 3 inch to 3 x 2 combi looking up for lav (clean out in combi below) you will have 2 vents

    [​IMG]
     
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  4. HiQ

    HiQ Member

    Joined:
    Jan 4, 2017
    Location:
    Manitoba
    Just trying to wrap my head around this. So can I get away with:

    Only the lav and tub are 1-1/2" dry vented off a shared 2" through the roof vent. WC is wet vented off lav. Home Depot up here doesn't really carry a lot of the combi fittings so I'll probably just use 3x3x1-1/2 wyes with 1-1/2 45 streets for lav and tub. WC on 4" flange with 4x3 closet bend into a 3" wye.

    I believe the existing bathroom is maybe 15-20' away so I guess I have the option of using the existing through the roof vent shared between both of these bathrooms assuming it's 3"? Not sure if it's easier to run a vent in the attic 15-20' or just blow a new 2" through the roof right above the 2x6 wall. See what he wants to do as he's taking care of sealing the vent through the roof properly.

    Thanks!
     
  5. Jeff H Young

    Jeff H Young In the Trades

    Joined:
    Feb 27, 2020
    Location:
    92346
    the lav would be described as dry vented though serving a wet vent for the w/c . I think 2 inch reducing to a 2 x1 1/2 x1 1/2 santee at the tub and lav is how I would do it though 1 1/2 is all you need
     
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  6. HiQ

    HiQ Member

    Joined:
    Jan 4, 2017
    Location:
    Manitoba
    Awesome. Thank you very much. He just messaged me that he found a 1 piece RHD drain tub/shower unit for $300. Cheap, but there goes the all on one wall dream scenario. Might get a little more tricky here shortly. I'll add another message if I get tripped up in the future. Thanks!
     
  7. Jeff H Young

    Jeff H Young In the Trades

    Joined:
    Feb 27, 2020
    Location:
    92346
    No big deal just use a 2 inch trap and arm (below joists). or lay a combi on side and go to otherside of tub and 90 up then put your santee on (vent will be 5 foot away other side of tub). its still a very simple and easy build
     
  8. HiQ

    HiQ Member

    Joined:
    Jan 4, 2017
    Location:
    Manitoba
    Very true. I was thinking about splitting the vent in the attic and running the drain on the tub parallel to the 3" and then wye'ing in once I turn the lav/wc 3" 90* towards the tub. It needs to ultimately head that direction to find the main stack. You way would be easier, but then I'd have to blow the 2" through all the joists as I don't want to go under them. That's fine as long as the joists are 2x12s which they really should be. I guess even 1-1/2" can run 6' before the vent, but that's be basically what I'd be at. Bumping up to 2" would be safer as you can be like 8' away? I'll keep it in mind as I'm going to check out what he has tomorrow. Thanks again!
     
  9. Jeff H Young

    Jeff H Young In the Trades

    Joined:
    Feb 27, 2020
    Location:
    92346
    your main is already under the joists so no issue ? running a seperate 2 inch or 1 1/2 parraell to the 3 inch could be done, dont know about attic work? that not hard to connect 2 vents together. so yea another option
     
  10. HiQ

    HiQ Member

    Joined:
    Jan 4, 2017
    Location:
    Manitoba
    The lav/WC 3" will be tucked up in the joist space. Once it gets past the tub it will 90* and follow a bulkhead under the joists. Not sure if I'm explaining this well. I'll grab some pics or draw something up in the future. Thanks.
     
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