1. Larry4

    Larry4 New Member

    Messages:
    24
    I will be plumbing in one island sink with a disposal attached. The island is only 6 feet horizonally from soil line below floor. If I oversize the drain below to 3" to the soil line will that act like a combo waste and vent. I was going to ask the inspector but didnt know if it was a total no no.

    thanks ,

    lar
  2. nhmaster

    nhmaster Master Plumber

    Messages:
    3,189
    Location:
    S. Maine
    It is an absolute yes yes. And a seldom used and often over looked option.
  3. Redwood

    Redwood Master Plumber

    Messages:
    7,453
    Location:
    Connecticut
    I don't care much for oversizing the kitchen sink drain. With 3" there is a lack of scouring and when they clog they are a bear to get clean.
  4. nhmaster

    nhmaster Master Plumber

    Messages:
    3,189
    Location:
    S. Maine
    I've never run into that. I have run a 3" right up into the base cabinet and connected there. I usually put a 3" wye and ECO under the floor but I can't remember ever having to clean it them out.
  5. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,285
    Location:
    Cave Creek, Arizona
    drain

    Maybe you won't but someone will someday. Whether it is permitted or not depends on the local jusidiction. Sometimes they will let you run a 3" horizontal line and then tie both the drain and the vent into the top of it as a modified waste and vent.
  6. nhmaster

    nhmaster Master Plumber

    Messages:
    3,189
    Location:
    S. Maine
    IPC will let you run it horizontal, come vertical through the cabinet base, 3" elbow with a 3 x 1 1/2 bushing. Miles better in my opinion than an island vent or a AEV.
  7. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego

    Under CA code (UPC) combination waste/vent systems are ONLY for showers and floor drains. They are NOT allowed for sinks or other fixtures roughed in above the floor. 2007 CA Plumbing code, 910, and appendix B2.
  8. nhmaster

    nhmaster Master Plumber

    Messages:
    3,189
    Location:
    S. Maine
    Ahhhhhh.. California sucks. :D
  9. Larry4

    Larry4 New Member

    Messages:
    24
    thank You!
  10. SewerRatz

    SewerRatz Illinois Licensed Plumber

    Messages:
    1,706
    Location:
    Chicago, IL
    The best way to vent an Island sink is as pictured.

    [​IMG]
    Last edited by a moderator: Nov 29, 2008
  11. kingsotall

    kingsotall Plunger/TurdPuncher

    aka "loop vent"
  12. nhmaster

    nhmaster Master Plumber

    Messages:
    3,189
    Location:
    S. Maine
    I dissagree. the loop vent is the most complicated, most likely to plug the vent and never get cleaned out and most complicated mess ever dreamed up. Much as I hate them, I'd use an AAV long before I would pipe that monstrosity ever again.
  13. SewerRatz

    SewerRatz Illinois Licensed Plumber

    Messages:
    1,706
    Location:
    Chicago, IL
    Sadly, the AAV,s are not allowed here in Illinois. The loop vent is the only option we have here. Properly installed I have never had any issues with them.
  14. Redwood

    Redwood Master Plumber

    Messages:
    7,453
    Location:
    Connecticut
    What is so sad about AAV's not being allowed there.
    IMHO the place they belong is in the trailer park on the badly plumbed trailers.
  15. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,285
    Location:
    Cave Creek, Arizona
    vent

    We called them "yoke" vents because they look like the device that is used to hold cattle. But that type of vent WILL let the sink drain until such time as the relief vent goes underwater. An AAV will stop draining as soon as ANYTHING blocks the connection to the main. An AAV therefore will give the impression of a blocked sink drain, when the real cause could be a blocked,or blocking, main sewer, leading to a misdiagnosis of where the problem is.
Similar Threads: island vent
Forum Title Date
Plumbing Forum, Professional & DIY Advice, Tips & Problem with very old island loop vent --- should I replace with AAV? May 3, 2014
Plumbing Forum, Professional & DIY Advice, Tips & Unique island vent situation Apr 28, 2014
Plumbing Forum, Professional & DIY Advice, Tips & Venting island/washer/crapper Mar 25, 2014
Plumbing Forum, Professional & DIY Advice, Tips & Possible vent issue on a kitchen island with kitchen sink in it Feb 2, 2014
Plumbing Forum, Professional & DIY Advice, Tips & non-island loop vent Oct 30, 2013

Share This Page