When to use 2x6 to allow for plumbing (interior walls)

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by ginahoy, Mar 10, 2014.

  1. ginahoy

    ginahoy Building Systems Engineer

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    Dec 23, 2006
    Location:
    Sierra Vista, AZ
    As mechanical systems designer, I work with plans a lot. I often see 2x6 interior walls for plumbing but it's not consistent. I think architects and designers learn someone along the way to show 2x6 in certain situations but don't really understand when to apply, so they overdo this detail.

    In a single floor home, the only wall I imagine might need to be 2x6 would be behind a washing machine, to accommodate one of those recessed plastic drain panels. Even then I don't see why that wouldn't work with a 2x4 wall. In a two floor home, I can see how the primary drain from the upstairs fixtures would require a 2x6 wall on the lower floor. But I'm just guessing.

    Please elucidate me ;)
     
  2. Terry

    Terry Administrator Staff Member

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    Occupation:
    Plumber
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    Bothell, Washington
    If you have a 3" waste line, 3.5" OD and larger than that for the hub of the fitting, then it's nice to place that in a 2x6 wall. It doesn't bend the drywall to fit around the fittings.
    If you are running 2.0" and 1.5" lines, then 2x4 is fine. A washer box fits in the 2x4 spacing.

    It's nice that exteriors are going 2x6 now. So many times with the older homes, the wall was pretty badly swiss cheesed getting the kitchen plumbing in.
     
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  4. ginahoy

    ginahoy Building Systems Engineer

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    Dec 23, 2006
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    Thanks for quick reply. I advise clients to avoid any plumbing in exterior walls, but all of my clients are building high performance homes so 2x6 is pretty much standard. I guess my question is when would there ever be a 3" waste line in a wall on a single floor home? Shower, tub and toilet waste lines go down, not into the wall. Would a 3" drain line be required for a double vanity?
     
  5. hj

    hj Moderator & Master Plumber Staff Member

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    The exteriors are going to 6" walls for increased insulation R value, they could care less about how the plumbing will be installed. SOme areas require a "full size" vent line all the way to the roof. In our area, meaning yours and mine, they require the aggregate areas of all the vent pipes to be the equal to the area of the incoming sewer pipe.
     
    Last edited: Mar 10, 2014
  6. Terry

    Terry Administrator Staff Member

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    Plumber
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    Bothell, Washington
    2" is used for a double vanity.

    Almost never with UPC. I don't think I've ever done a 3" vent on a single floor home. I need something like two 2" vents and a single 1.5" vent and I'm good. If things are spread out a bit, maybe more vents.
     
    Last edited: Jun 14, 2017
  7. ginahoy

    ginahoy Building Systems Engineer

    Joined:
    Dec 23, 2006
    Location:
    Sierra Vista, AZ
    Thanks for confirming what I suspected.

    In most cases I'm able to do a plan review well before ground breaking to ensure HVAC has been accommodated, and optimized when possible. I have also been advising clients to have a plumbing contractor review their plans, especially regarding DHW and hot water distribution. This will ensure a reasonable solution for waste lines and vents.
     
  8. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    If someone wants a wall-hung toilet, you have more options if that wall is 2x6" construction.
     
  9. bob13bob

    bob13bob New Member

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    Jun 14, 2017
    Location:
    San Jose, CA
    they ahve gerberit toilet carrier frames (wall mount) for 2x4 and 2x6 walls. i find 2x6 preferable though.



    from 94 ubc i have on reference, you may want to refer to a newer version that's adopted by your local code.
    Sec. 2326.11.7. Pipes in Walls. Stud partitions containing plumbing, heating, or other pipes shall be so framed and the joists underneath so spaced as to give proper clearance for the piping. Where a partition containing such piping runs parallel to the floor joists, the joists underneath such partitions shall be doubled and spaced to permit passage of such pipes and shall be bridged. Where plumbing, heating or other pipes are placed in or partly in a partition, necessitating the cutting of the soles or plates, a metal tie not less than 0.058 inches (1.47 mm)(16 gage galvanized) and 1 1/2 inches (38 mm) wide shall be fastened to each plate across and to each side of the opening with not less than six 16d nails.
     
    Last edited: Jun 14, 2017
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