Size of hole for (hot water) waste pipe

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by Taylor, Jun 21, 2005.

  1. Taylor

    Taylor New Member

    Messages:
    143
    Location:
    Northern Joisey
    Quick question: how much leeway does a hole for DWV have to allow for expansion of the pipe?

    Installed i-joists under tub expressly for flexibiliity with holes. However the guy who speced them out for me gave me 9-1/2" instead of 11-/7/8", that's a difference of 2" hole vs 4" hole allowed where waste pipe would go. He must have been figuring it was enough for 1-1/2" tub drain, but in fact a 1-1/2" sch 40 DWV pipe leaves about 1/16" to 1/8" leeway around a 2" hole. Do I have anything to worry about when hot tub/shower water goes through that pipe?

    I know not to mess with specs on these i-joists, unlike dimensional lumber they just collapse when overloaded.
  2. srdenny

    srdenny Plumbing Contractor

    Messages:
    361
    Location:
    SF Peninsula
    Run the trap arm in DWV copper. At 1-5/8" od it will have plenty of space to move unimpeeded.
  3. Taylor

    Taylor New Member

    Messages:
    143
    Location:
    Northern Joisey
    Copper is not really an option. PVC waste pipe already lead-soldered to waste stack (by plumber) and there isn't room enough for a PVC/copper coupling. I haven't drilled the hole for the waste pipe through the joist yet, I'm pretty sure that by doing it very carefully I can get a 2" hole spot on. I had to replace a joist that among other things had a 3" hole, too big....

    I think there was a thread here recently about copper waste pipes crumbling due to use of cleaners....
  4. Taylor

    Taylor New Member

    Messages:
    143
    Location:
    Northern Joisey
    Well called TrusJoist and I'm still okay for expected load with 2'6" hole, because of short span, so I can enlarge that hole a bit.

    Edit: Make that 2-1/2" hole....
    Last edited: Jun 21, 2005
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