Results 1 to 14 of 14

Thread: Vent Stack Size

  1. #1
    Join Date
    Mar 2007
    Location
    Spring City/Surrounding Philadelphia area
    Posts
    3,471

    Default Vent Stack Size

    Attached is a pic from the rear of a house I looked at yesterday. In the pic I circled the only plumbing vent pipe I noted at the house and it was about a 2" copper pipe. What is the minimum size vent pipe a house should have for adequate venting of the plumbing system? The house had one bathroom and it was on the upper level adjacent to the kitchen. I did get some gurling from the bathroom sink drain when it was emptying so I wouldn't be surprised if this vent pipe is undersized. The vent pipe exits the house below the bathroom. Shouldn't there be another vent closer to or above the bathroom?

    Similar Threads:
    ***IMPORTANT*** You Need To Register To View Images ***IMPORTANT*** You Need To Register To View Images
    Inspection Referral SOC

  2. #2
    Join Date
    Mar 2007
    Location
    Healdsburg, CA
    Posts
    1,741

    Cool Re: Vent Stack Size

    It's wrong Nick, which you already suspect. Recommend an evaluation by a state licensed plumbing contractor because drainage system venting is an engineered process in which you should not have to guess the number and size of the venting system. The gurgling sound was an excellent piece of evidence that things where not right.
    UPC Chapter 9 and IRC Chapter 31.

    Jerry McCarthy
    Building Code/ Construction Consultant

  3. #3
    David Banks's Avatar
    David Banks Guest

    Default Re: Vent Stack Size

    Plumbing code in MA says this.

    "The vent extension through a roof shall not be less than 2 inches in diameter and shall extend not more than 24 inches and not less than 18 inches through the roof.
    FROST CLOSURE: Where frost closure is likely to occur, each vent extension through a roof shall be at least three inches in diameter.
    PLUMBING VENT STACK EXTENSIONS OUTSIDE THE BUILDING: All soil, waste or vent pipe extensions shall be installed inside the building. For remodeling vents may be installed outside the building with permission of local inspector"


  4. #4
    Join Date
    Mar 2007
    Location
    Healdsburg, CA
    Posts
    1,741

    Default Re: Vent Stack Size

    All soil, waste or vent pipe extensions shall be installed inside the building.
    That can't be right???

    Jerry McCarthy
    Building Code/ Construction Consultant

  5. #5
    Join Date
    Mar 2007
    Location
    Philadelphia PA
    Posts
    3,177

    Default Re: Vent Stack Size

    Quote Originally Posted by Jerry McCarthy View Post
    All soil, waste or vent pipe extensions shall be installed inside the building.
    That can't be right???
    Not terminate inside the building.

    "There is no exception to the rule that every rule has an exception." -James Thurber, writer and cartoonist (1894-1961)
    www.ArnoldHomeInspections.com

  6. #6
    Join Date
    Mar 2007
    Location
    Ormond Beach, Florida
    Posts
    25,317

    Default Re: Vent Stack Size

    Quote Originally Posted by Jerry McCarthy View Post
    All soil, waste or vent pipe extensions shall be installed inside the building.
    That can't be right???
    That's 'inside the thermal envelope', or else they need to be insulated or have heating tape, or both, on them.

    That freeze line is basically along Jacksonville, Florida, to Tallahassee, to Pensacola, across to Texas and up and around, it's in the Appendix to the plumbing code.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  7. #7
    David Banks's Avatar
    David Banks Guest

    Default Re: Vent Stack Size

    I assume they meant this.

    ***IMPORTANT*** You Need To Register To View Images ***IMPORTANT*** You Need To Register To View Images

  8. #8
    Join Date
    Mar 2007
    Location
    Ormond Beach, Florida
    Posts
    25,317

    Default Re: Vent Stack Size

    Quote Originally Posted by David Banks View Post
    I assume they meant this.
    Yep.

    Not only does that pipe need to be protected from physical damage, it needs to be protected from freezing (the part under discussion here).

    I don't see a support or strap for the offset or the top section of pipe (is there a strap at the top?, looks like it's next to a gutter and has nothing to strap to).

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  9. #9
    Join Date
    Mar 2007
    Location
    Healdsburg, CA
    Posts
    1,741

    Default Re: Vent Stack Size

    In the pic I circled the only plumbing vent pipe I noted at the house and it was about a 2" copper pipe. What is the minimum size vent pipe a house should have for adequate venting of the plumbing system?
    Aside from what has been addressed so far what about the minimum sized vent stack? Table 3005.4.1.

    Jerry McCarthy
    Building Code/ Construction Consultant

  10. #10
    David Banks's Avatar
    David Banks Guest

    Default Re: Vent Stack Size

    IRC- P3103.2 Frost closure. Where the 97.5-percent value for outside design temperature is 0 degrees F or less, every vent extension through a roof or wall shall be a minimum of 3 inches in diameter. Any increase in the size of the vent shall be made inside the structure a minimum of 1 foot below the roof or inside the wall.

    Table P3107.3 Common Vent sizes- Vent sizes 1 1/2-3 inches.

    Other tables show up to 4 inches depending on number of fixture units.

    Easy for me as I will just use MA Plumbing code above as my guideline


  11. #11
    Joshua Hardesty's Avatar
    Joshua Hardesty Guest

    Default Re: Vent Stack Size

    For one full bath and one kitchen, a 2" vent should be plenty. However...

    If that vent enters the home between the first and second floor, then that can't be venting the sink. I'm assuming there's no AAV attached to the sink in the bathroom. I'd be more willing to bet that it's gurgling because the sink's not vented at all and on an S-trap more than the fact that it's "only" a 2" vent.


  12. #12
    Join Date
    Apr 2007
    Location
    state of jefferson
    Posts
    520

    Default Re: Vent Stack Size

    here every fixture requires protection from a trap and vent. the area of all the vents are required to meet or exceed the area of the sewer pipe serving the building. something technical to do with equal pressure etc..


  13. #13
    Joshua Hardesty's Avatar
    Joshua Hardesty Guest

    Default Re: Vent Stack Size

    So, if you have a single bath house, and have a 3" line, you need a 3" or greater vent through the roof?


  14. #14
    Join Date
    Apr 2007
    Location
    state of jefferson
    Posts
    520

    Default Re: Vent Stack Size

    yes. a three inch vent is required


Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •