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  1. #1
    Join Date
    Nov 2013
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    Default Clogged Island sink vent

    I have a clogged island sink. I have snaked the sink 10 feet, I have checked the P-trap it was all clear. When I opened the clean out, there is a sucking sound and the sink immediately drains. I tried blowing air back through the vent and it worked for a few minutes but stopped working again. I suspect the vent is clogged. Does anyone know how to clear the vent in an island sink?

  2. #2
    Join Date
    Jul 2010
    Location
    SoCal
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    5,066

    Default Re: Clogged Island sink vent

    Without knowing how your plumbing is set up, it's hard to recommend. I have a feeling that your blockage is past the clean out.

    Call a drain plumber, who has a better snake.

  3. #3
    Join Date
    Jan 2008
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    1,093

    Default Re: Clogged Island sink vent

    It does sound like a vent issue, possible combined with a partial drain clog somewhere downstream. Being an island sink, this is likely a studor vent. If you follow the vent under the sink you'll see a stub reaching to under the countertop where it stops. If it's PVC or ABS piping, the vent apparatus should unscrew from the adapter, allowing you to snake that pipe and inspect/replace the vent. To test the vent, run a sink of water down the drain with the vent off. Be sure the water level in the sink is lower than the top of the vent pipe when you do this! If it drains correctly the vent unit is bad, screw a new one on in it's place. Take with you the old one to match threads. It's also possible the vent was installed improperly- it should be vertical and as high as possible under the countertop.

    Sometimes these are placed in island backsplash walls in which case you're going to have to open the wall to access the vent if it needs replacement. To test an inaccessible studor vent, disconnect the drain and isolate the vent pipe. Use the suction side of a shop vac to check for airflow- it shouldn't restrict the flow and the vacuum shouldn't sound strained. Reverse the flow and there should be loss of airflow and the vacuum cleaner should be straining to work. It's simply a one-way air valve.

    Studor vents are simple and not likely to get out of order but anything is possible and the are not immune to clogging if any debris finds it's way inside restricting the movement of it's valve. BTW, studor vents are not supposed to be inaccessible by code, but since they rarely give trouble that is a common practice in remodeling work and it's often done with islands in order to get the vent higher than the sink, it's best location.

    Phil

  4. #4
    Join Date
    Dec 2013
    Location
    Montreal Canada
    Posts
    93

    Default Re: Clogged Island sink vent

    vents are supposed to go 6 inches above the flood level rim of the fixture before changing direction, but what about islands sinks. I usually over size drains of island sinks and install an auto air vent that will allow air to entrance only on negative pressure. I would install one of these auto air vents here.

  5. #5
    Join Date
    Jan 2008
    Posts
    1,093

    Default Re: Clogged Island sink vent

    Quote Originally Posted by bill shack View Post
    vents are supposed to go 6 inches above the flood level rim of the fixture before changing direction, but what about islands sinks. I usually over size drains of island sinks and install an auto air vent that will allow air to entrance only on negative pressure. I would install one of these auto air vents here.
    Bill, in the industry "auto air vents" are all generically called "Studor vents" after the first company to make them, even though many different firms make them now. Similar with "Fernco connectors", it's the name everyone in the business uses no matter who makes 'em.

    In old houses, a lot of stuff that works well enough doesn't meet today's codes. As long as a vent won't flood closed it will work fine it is big enough, runs uphill, and is open. Plus a lot of "wet vents" twist and turn long before they're 6" up above their starting point.

    Phil

  6. #6
    Join Date
    Dec 2007
    Location
    Tennessee
    Posts
    1,381

    Default Re: Clogged Island sink vent

    Not every one uses a Studor vent in their island. The island can be vented by running the vent line up to the bottom of the counter, make a U-turn, and go under the foundation or floor to the nearest vent riser in a wall. If this somehow got filled with water for some reason, i.e rainwater, then it would stop working. The best answer would be to cut off the U-bend, cap the vent pipe going under the floor and put in a Studor vent.

  7. #7
    Join Date
    Jan 2008
    Posts
    1,093

    Default Re: Clogged Island sink vent

    Quote Originally Posted by keith3267 View Post
    Not every one uses a Studor vent in their island. The island can be vented by running the vent line up to the bottom of the counter, make a U-turn, and go under the foundation or floor to the nearest vent riser in a wall.
    Run that way, any plumber would see that this is creating a trap- not a good idea in a vent line and not allowed by even the moist basic plumbing codes. Not to say it's never happened- you never know what you'll run into in this business!

    Phil

  8. #8
    Join Date
    Dec 2007
    Location
    Tennessee
    Posts
    1,381

    Default Re: Clogged Island sink vent

    Quote Originally Posted by Mastercarpentry View Post
    Run that way, any plumber would see that this is creating a trap- not a good idea in a vent line and not allowed by even the moist basic plumbing codes. Not to say it's never happened- you never know what you'll run into in this business!

    Phil
    Thats exactly how they did it on the TOH Napa Valley project. It would be OK if they tapped into a vent pipe that went all the way down into the drain line, like they did on the Napa Valley house, but if they just ran the vent line up without this, then it would be a problem.

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