4 inch or 3 inch pipe?

Discussion in 'IPC Plumbing Code Questions' started by mailman62, Jan 3, 2015.

  1. mailman62

    mailman62 New Member

    Joined:
    Jan 2, 2015
    Location:
    Rhode Island
    planning layout forbath with toilet,sink and shower, connecting waste line to cast iron pipe that looks like 4 inchs, was going to use 4 in pipe to this but is that a overkill or would 3inch pipe be better
     
  2. Terry

    Terry Administrator Staff Member

    Joined:
    Aug 17, 2004
    Occupation:
    Plumber
    Location:
    Bothell, Washington
    3" pipe is fine. I don't go to 4" until I bring in a forth toilet.
     
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  4. mailman62

    mailman62 New Member

    Joined:
    Jan 2, 2015
    Location:
    Rhode Island
    will go with 3in , also what size do you recommend for vent thru roof off of this 3in waste line ,3in or 2in?, live in ri if that matters. thanks
     
  5. hj

    hj Master Plumber

    Joined:
    Aug 31, 2004
    Occupation:
    Plumber
    Location:
    Cave Creek, Arizona
    In most areas, since you should already have the required vent sizes through the roof, 2" is adequate.
     
  6. Sylvan

    Sylvan Still learning

    Joined:
    Sep 23, 2004
    Occupation:
    plumbing - fire suppression - boiler inspector
    Location:
    New York
    Since your in Rhode Island ( I was stationed in New Port in 1968) I know it gets really cold up there so I would go with a 4" vent through the roof (VTR) to prevent hoarfrost as I have seen to many 3" vent blocked with ice
     
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