You were given incomplete information. While studor vents/air admittance valves are allowed by many codes, they do not nor should they replace a main vent. According to code here, AAVs can be used on a fixture, BUT the plumbing system must STILL be vented at some point to the open atmosphere by means of a main vent.
I also agree that AAVs aren’t the best choice in most circumstances. They DO fail as nothing lasts forever. If your vent stack or stack vent is failing, replacing it is the correct way to remedy the problem.
» This message has been edited by CincinnatiPlumbing on 20 April 2005