Kitchen sink (island) employs an Air Admittance Valve instead of the traditional Vent Stack. Installation is about 1 year old. Recently, foul odors emanate from the sink drain after a small quantity of water is drained. If a large quantity of water goes down the drain, there are no odors. Could this mean that the Air Admittance Valve is not closing properly ?
Replace it and you will be ok.Unless you are handy and want to install a loop vent ,go ahead,but the auto air vent will work just fine. I would suggest changing it when you notice it is going bad.