Thread: Bathroom Drain Vent

I've been noticing a foul smell when I turn on the water in our second bathroom. I looked under the sink, and the drain vent comes up higher than the trap, but the vertical vent pipe ends under the sink with a slotted cone cover over the end of the vent. Aren't drain vents supposed to tie into the vent stack that goes up to above the roof, and tie in at a point higher than the the level of the sink?

Similar Threads:

• PVC drain lines
• Secondary drain setup
• lead drain
• condensate drain routing
• condensate drain connection

Originally Posted by Jim Shannonhouse

I've been noticing a foul smell when I turn on the water in our second bathroom. I looked under the sink, and the drain vent comes up higher than the trap, but the vertical vent pipe ends under the sink with a slotted cone cover over the end of the vent. Aren't drain vents supposed to tie into the vent stack that goes up to above the roof, and tie in at a point higher than the the level of the sink?

You are describing an Air Admittance Valve (AAV).

From your description, I would say that it was: a) installed wrong; b) not installed correctly; c) installed not as it should have been installed; d) or is defective and needs to be replaced.

Usually, from my experience, d) is caused by a), b), or c).

If it is black then it is the wrong AAV. and has failed.
Replace with code accepted AAV.

Many times small insects like spiders get caught in the seal of the valve, with most of the AAV's I have dealt with you can unscrew the top of the valve and flush them out with water.