bathroom odor

Good pic.

In most household sink installations, there is T on the waste line that goes up a vent pipe. It's usually buried in a wall so you don't see it though. Sinks that are in islands and some other locations can't do this   so they use an "air vent" or "utility vent", which allows for the limited passage of air but seals up when not needed.

The picture you see is under the sink and the vent is the little black screw-on fitting at the top of the pipe. It has a little flapper in it. If it doesn't work properly you get gray-tank gasses coming up inside the sink cabinet. It is not a pleasant smell. It is an easy fix.

Originally posted by shroomer Good pic. In most household sink installations, there is T on the waste line that goes up a vent pipe. It's usually buried in a wall so you don't see it though. Sinks that are in islands and some other locations can't do this   so they use an "air vent" or "utility vent", which allows for the limited passage of air but seals up when not needed. The picture you see is under the sink and the vent is the little black screw-on fitting at the top of the pipe. It has a little flapper in it. If it doesn't work properly you get gray-tank gasses coming up inside the sink cabinet. It is not a pleasant smell. It is an easy fix.