Is this Air Admittance Valve Installed Correctly?

D107

This tiny half-bath sink was put in 16 years ago and it's never drained right. Drains slow, bubbles up at draining's end. Just replaced the old AAV and found much crud in valve and pipe leading to valve. But I noticed that while the height of the valve is more than 4 inches, it is still way below the bottom of the sink. Should I get an extender in there and get above the bottom of the sink? (The valve is straight up despite the photo appearance.)

Larry Weingarten

Hi, In an ideal world, the AAV would be above the flood rim of the sink. I'm imagining that the valve where it is, is often under some slight pressure, and may be sticking closed. Raising it up could only do good things, and likely keep the AAV cleaner. As the slow draining problem has existed since the start, how is the rest of the drain line? Any possible problems there? 🤔

Yours, Larry

D107

@Larry Weingarten It's quite good in most of the rest of the house—the basement slop sink sometimes gets slow but I just cleaned its AAV and now drains fine. I know the pictured sink's drain is quite small <2" so that doesn't help.

Larry Weingarten

Hi @D107, I'm a fan of AAVs. Used them in my home built over 20 years ago, and they are working fine. Still needed a main stack vent through the roof, but no other roof penetrations. I worried that the AAVs might leak, so put them as high as possible and above highest water line where I could. The height might be keeping junk from the valves. 😎

Not sure it's worth the effort, but you could remove the vent and extend the pipe up with some sort of hose. Then see if the sink drains any better…

Yours, Larry