Venting Above Flood Rim?

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by Kathristin, Oct 12, 2008.

  1. Kathristin

    Kathristin New Member

    Joined:
    Aug 15, 2008
    I know the plumnbng code in NJ and probably most other states require that the vent connection be at least 6" above the flood rim before continuing horizaontally. I am just curious as to why 6". What is the hydraulics behind this rule?

    Also, is it 6" as measured to the centerline of the horizonal run?

    Thanks
     
  2. jimbo

    jimbo Plumber

    Joined:
    Aug 31, 2004
    Location:
    San Diego, CA
    The rule is there so that there would never be a case where a clogged fixture would cause water. and presumably some waste..to back into the vent line and clog it. I think the 6" number was just chosen as a good number. I can't tell you right off hand if it is measured to C/L or to the weir of the fitting. If you are close, an inspector will probably not give you any grief.
     
  3. Sponsor

    Sponsor Paid Advertisement

     
  4. hj

    hj Moderator & Master Plumber Staff Member

    Joined:
    Aug 31, 2004
    Occupation:
    Plumber
    Location:
    Cave Creek, Arizona
    vent

    The other part of the sentence which you did not quote, is usually "or 42" above the floor whichever is HIGHER". This is because a 36" high kitchen sink might be attached at some later date and this would require it to be 42" to comply with the 6" rule. The 6" measurement is to the flow line of the horizontal pipe, and was probably determined in a laboratory using a vacuum pump to simulate some theoretical situation, such as a high rise building.
     
Similar Threads: Venting Above
Forum Title Date
Plumbing Forum, Professional & DIY Advice Venting line above window Dec 19, 2013
Plumbing Forum, Professional & DIY Advice Is my venting adequate for what I have Tuesday at 10:22 AM
Plumbing Forum, Professional & DIY Advice Venting question on a double lav on outside wall. Tuesday at 9:13 AM
Plumbing Forum, Professional & DIY Advice Venting Saniflo. Much confusion Mar 15, 2017
Plumbing Forum, Professional & DIY Advice Proper venting of washing machine and sink drain in basement Mar 13, 2017

Share This Page