Bathroom sink venting question

I recently remodeled my bathroom. I added a sink where there never was one. It's a very old house that used to be a three plex. There was a drain from one of the old kitchens so I tapped off of that for the drain.

I bought one of those under the counter vents with the rubber diaphram. Well I believe there is a flaw in the design. I have the trap before the vent and the vent is coming off the drain using a T fitting and a 90 to run it up about 12 inches. The tube fills with water blocking the diaphram.

Any ideas to help with this? I'm sure it's a simple fix I just can't see it.

Thanks, jeremy

Well, we do not like air admittance valves. But they are legal in SOME places. We would like a pic of your installation, but in general...a "tube filled with water"......would indicate a clogged drain. The vent is a different issue, but nothing should fill with water, vent or not.

Blockage. Drain needs to be rodded.

No there is no plug in the line. It drains fine without the valve in place but after 10 or 15 seconds the pipe starts to fill. Theadded on pipe for the valve fills. Otherwise it drains straight down. I'll see if I can get some pics of the area.

jeremy

vent

The line is plugged, which is why it will not drain with the AAV installed and drains but fills with water when it is removed. Also, you terminology of where you have the AAV, "trap before the vent", may be ambiguous. Do you have it between the sink and the trap, or the trap and the pipe in the wall?