Slow Draining Sink except when AAV is removed...

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by mdistel, Aug 14, 2007.

  1. mdistel

    mdistel New Member

    Messages:
    2
    If I untwist one of the Oatey Air Admittance valves under either the main kitchen sink or the island sink the sink drains normally. Otherwise I hear gurgling, usually in the island sink. I put a plastic bag over the AAV pipe and unscrewed the AAV, the bag filled with air when I ran the sink. Isn't an AAV supposed to allow air in, not out? What is the likely problem?

    Mark
  2. cwhyu2

    cwhyu2 Consultant

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    Cincinnati OH
    you might have slow drain or stoppage.
  3. try a new AAV

    It could be the AAV going bad....

    but their is a better chance that the drainline is
    beginning to get stopped up.....

    probably need to clean it out and see if that solves the issue
  4. hj

    hj Moderator & Master Plumber Staff Member

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    aav

    YOu are correct in that the AAV lets air in, but not out. That is your problem. Air is being trapped in the pipe, and since the air cannot be vented because of the AAV, the water either cannot drain, or cannot drain very fast.
  5. GrumpyPlumber

    GrumpyPlumber Licensed Grump

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    mdistel,
    If you don't hear a suctioning sound while the vent is in place...replace it.
    Look for a "Studor" vent.
    If the problem where positive pressure, you'd likely have overspill when the vent were removed.
    You could do a simple test by putting your hand over the hole while the sink is draining.
  6. frenchie

    frenchie Jack of all trades

    That's not making sense to me, Grumpy.

    If the bag's filling with airl... by definition... that's positive pressure, isn't it?

    Are you using those words in some specialized, plumber-ese, technical sort of way or something?
  7. GrumpyPlumber

    GrumpyPlumber Licensed Grump

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    There's likely a mechanical vent there because the drain drops into the floor after the trap.

    When the waste water drops, it creates a suction...not positive pressure...without a vent for the vacuum it drains slower.
  8. hj

    hj Moderator & Master Plumber Staff Member

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    Location:
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    drain

    He already stated that there is an AAV. Suction/vacuum speeds up drainage. Vents stop vacuum thus slowing drainage rate down to whatever the water's head pressure will generate. Positive pressure slows or stops drainage.
  9. GrumpyPlumber

    GrumpyPlumber Licensed Grump

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    I missed the part about the bag filling...geesh.
    Ten to one the drain is either undersized, or blocked.
    Last edited: Aug 16, 2007
  10. GrumpyPlumber

    GrumpyPlumber Licensed Grump

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    Also...why wasn't the island bow vented?
  11. mdistel

    mdistel New Member

    Messages:
    2
    Thank you for all the replies. Both the island and the main sink are vented. I'll have to have a plumber come sank the lines, I tried and didn't get anywhere. Now I need to find a good plumber in the Cleveland area.

    Mark
  12. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
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    Location:
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    vent

    For the same reason AAV's are used anywhere. It is cheaper. But if the drain line is plugging, then a bow/loop vent will give the same symptoms as an AAV.
  13. GrumpyPlumber

    GrumpyPlumber Licensed Grump

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    Right, I keep forgetting mechanical vents are allowed in some states.
    Here bow vents are an art...we take pride in them.

    If this work was done on the cheap, then I'm putting my money on the common drain being 1-1/2", maybe 1-1/4".
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