Sanitary Tee vs. 90 Wye vs. Vent Tee
Downstream from my sink trap I am required to vent the drain - I am accomplishing this with a studor (air emittance) valve. In order to install this valve I must tee into the horizontal line. Which fitting do I use in this instance? I have been told a sanitary tee is not to code but also recall that a wye is not to be installed 'laying on its back'. That leaves only the vent tee but I think that is also a misapplication. If the wye is the correct answer, in which orientation is it to be set? Help!
From the "Inspector is Always Right" Dept.
My local inspector prefers a san tee on its back to a wye/combo for vertical vent-only connections to a horizontal drain because "it vents better." No doubt backed up by extensive testing in his personal hydraulics lab (not). I'm sure the guy who replaces him will go around town hassling plumbers for installing san tees on their backs. So it pays to run your plans by your local inspector, especially if you're doing something for the first time, regardless of what code or common sense might otherwise suggest.
The Illinois Plumbing Code prohibits all mechanical venting including AAVs. Of course, all the home stores here sell Studor vents anyway--go figure.