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Thread: island vent

  1. #1

    Default island vent

    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. #2
    Master Plumber nhmaster's Avatar
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    Default

    It is an absolute yes yes. And a seldom used and often over looked option.

  3. #3
    Master Plumber Redwood's Avatar
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    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. #4
    Master Plumber nhmaster's Avatar
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    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. #5
    Moderator & Master Plumber hj's Avatar
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    Default 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. #6
    Master Plumber nhmaster's Avatar
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    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. #7
    Plumber jimbo's Avatar
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    Quote Originally Posted by larrygman View Post
    . 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

    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. #8
    Master Plumber nhmaster's Avatar
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    Ahhhhhh.. California sucks.

  9. #9

    Default

    thank You!

  10. #10
    Illinois Licensed Plumber SewerRatz's Avatar
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    The best way to vent an Island sink is as pictured.


    Nice picture of an Island Vent, Washington State UPC code
    Last edited by Terry; 11-29-2008 at 10:04 AM. Reason: Resized image

  11. #11
    Plunger/TurdPuncher kingsotall's Avatar
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    aka "loop vent"

  12. #12
    Master Plumber nhmaster's Avatar
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    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. #13
    Illinois Licensed Plumber SewerRatz's Avatar
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    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. #14
    Master Plumber Redwood's Avatar
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    Quote Originally Posted by SewerRatz View Post
    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.
    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. #15
    Moderator & Master Plumber hj's Avatar
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    Default 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.

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