Air Admittance Valve
Although air admittance valves are approved by most large code bodies they still are not allowed by every state or municipality. They are used too much as a short cut rather than a necessity. They are sometimes needed in todays complex building designs and unusual fixture layouts or locations, But one should not install something that can fail so easily and often just to save a dollar when there is a better and safer solution. I have already removed or replaced 5 AAVs during last month because they failed (stuck closed) and they all happened to be installed on washing machines. 2 of them I had to replace, but the others only required a couple ftgs, pipe and flashing and less than an 1 hr labor to vent them through the roof. One home owner was pretty upset to see it was that easy to vent properly, as now they have to replace 2 rooms of new pergo floating floor because of the water damage caused by an air locked drain.