I recently had my house supply water lines replaced. At that time I asked the plumber if he could rough in a sink in the garage. I was about to replace the insulation and seal up the sheetrock hole where he added the new pipes when I noticed the drain vent pipe goes about 5 feet up the inside of the wall and ends in a cap with two holes in it. If I seal up the wall do I run the risk of sewer gases building up inside the wall or high moisture build up?

Hey sbirk:

Sound like you may have an AAV there. That is an automatic vent. All is OK, as long as you provide acess to the AAV. Home depot/Lowes sell some great access panels. Some are plastic, others are metal...but fact is that all AAVs must be accessible for future replacement. These vents need to be replaced once in awhile. That does not make them inferior... just that they have mechanical parts (spring/washer) and sometimes need to be replaced.

Are these even allowed in your state? Can always ask a local plumbing inspector... just call local town/city inspector and tell him you are thinking of adding sink and you heard about AAVs... see what he says.

See pic. Below... should look something like this... usually threaded... get back to me? Mark

.