bathtub branch size question

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by Zenman, Mar 29, 2009.

  1. Zenman

    Zenman New Member

    Messages:
    58
    Location:
    New Jersey
    I have a question regarding the branch size for the bathtub. I have researched it and have found conflicting information both in books and on this forum. I'm under UPC and in the state of NJ. Attached is a plumbing riser that I submitted to the inspector.

    On the second floor bathtub, there is a 1.5 inch drain that has a 90 degree horizontal turn. Eventually when it meets up the lav branch (vanity sink) I was planning on upping it up to 2 inches.

    So my question is... is the 1.5 tub branch with the horizontal 90 (long sweep) acceptable?

    Any other comments or constructive criticisms are welcome.

    Attached Files:

  2. Zenman

    Zenman New Member

    Messages:
    58
    Location:
    New Jersey
    No takers?
  3. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,641
    Location:
    Cave Creek, Arizona
    drain

    It is acceptable, but I would not do it that way, just so my customers did not have premature drain stoppages.
  4. Zenman

    Zenman New Member

    Messages:
    58
    Location:
    New Jersey
    Thanks for your reply HJ. I see in other threads you have recommended 2 inch as well. I am considering it, but the problem is that the particular joist bay where the 90 elbow will be is very narrow. (Also if a different joist bay were used, two 90 elbows would be needed.) So I only have 4 inches between the joists and part of the long sweep 90 elbow will have to be inside the bored out joist - which means a lager hole - and this is why I am hesitant. I will test and see what fits in some scrap lumber I have.
  5. nhmaster

    nhmaster Master Plumber

    Messages:
    3,189
    Location:
    S. Maine
    If you must use a 90 get a long sweep.
  6. Zenman

    Zenman New Member

    Messages:
    58
    Location:
    New Jersey
    Yes, it will be a long sweep 90.
  7. Zenman

    Zenman New Member

    Messages:
    58
    Location:
    New Jersey
    more info...

    It gets a little confusing with different codes, but I'm searching on UPC and found that a bathtub drain is rated 2 DFUs. A vertical 1 1/2 inch pipe is good for 2 DFUs, however a horizontal 1 1/2 inch pipe is only good for 1 DFU. Which tells me that a 1 1/2 inch horizontal branch line is too small for my bathtub (under UPC.)

    After a bit of more research I found that "The UPC requires at least a 2-inch drain immediately beyond the trap." This is regarding bathtubs and some other fixtures (ie kitchen sink with disposal and dishwasher). Source: Code Check: Plumbing, Redwood Kardon, et al.

    In order for me to be code compliant, it looks like I need to go with a 2 inch branch line.

    Attached Files:

  8. cwhyu2

    cwhyu2 Consultant

    Messages:
    1,347
    Location:
    Cincinnati OH
    1"1/2 is fine for a tub,what the code says is combined fixture units.
    The portant out let of a lav is 1"1/4 min pipe size is 1"1/4 .
    The P/O of a tub 1"1/2 so min pipe size 1"1/2
    the more fixture units the larger the pipe.
    Tub is 2 F/U here.1"1/2 pipe.
  9. Zenman

    Zenman New Member

    Messages:
    58
    Location:
    New Jersey
    Thanks cwhyu2. I guess what I don't understand is the UPC T7-5 chart specifically where it says only 1 F/U is allowed on a 1 1/2" horizontal pipe. :confused:

    Oh yeah, nice car you have there cwhyu2.... looks like a '69 Mustang. Back in the '80's I had a couple of Mustangs - a '66 coup and a '73 Mach I... fun cars. :D
  10. kingsotall

    kingsotall Plunger/TurdPuncher

    Aren't isometric drawings so much easier to get an understanding of the piping layout. Great riser submittal, guess the geeky plumber in me is showing.
  11. Zenman

    Zenman New Member

    Messages:
    58
    Location:
    New Jersey
    As someone once said, a picture is worth a thousands words. I have a CAD background and drew it up fairly quickly on the computer. I have found that I can draw a picture to explain something much faster than using words.

    I'm not sure the plumbing inspector will actually look at the ISO before he comes to inspect, so that's why I figured I would ask questions here first. He is hard to get a hold of, so I have not had a chance to ask him what he thought. Also some inspectors just want to say Pass or Fail. Which I totally understand, since they are not paid to design my layout. So I really do appreciate everyone's input on this forum.
  12. cwhyu2

    cwhyu2 Consultant

    Messages:
    1,347
    Location:
    Cincinnati OH
    Mach1,351W,4v,325hp,been modified some but mostly real.FMX auto.3.25to 1
    rear end,And it is a blast,Pony cars rock!
  13. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,641
    Location:
    Cave Creek, Arizona
    drain

    Sometimes it is a judgement call by the inspector. Here, many, if not most, above the ground tub wastes are 1 1/2" and some under the slab ones are also.
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