Originally Posted by iamgrowler
Okay, these are some common uses of a Wye, Combo and Wye branch from a groundwork about a year or so ago.
#1) is a 'Combo', which is a preassembled Wye branch and eighth bend. You can make your own combo by putting an eighth bend (a 45) into a wye.
#2) is a 'Reverse Combo', where the eighth bend is transitioned from vertical to horizontal.
#3) is an acceptable transition from horizontal to horizontal.
#4) is an example of the vent taking off vertically above the centerline of the waste line.
#5) is another example of an acceptable transition from horizontal to horizontal.