Normally it takes two of these
Notice the stainless steel wrap that prevents the pipe from shifting?
I'm investigating how to insert a sanitary tee into an existing vertical 3" stack that will not budge at all (vertically). One of the discussions I found here suggested cementing the lower part of the santee and using a fernco fitting for the top part. Is this the recommended method or are there better alternate methods?
If it does not move, there is no way you could "cement the bottom and use a transition coupling on the top", because you would have to cut out enough pipe to angle the Y in, then slide it down, and then whatever you are using would be too short to fill the gap.
Licensed residential and commercial plumber
To clarify, the cut stack can be moved enough in the x-y direction, just not up and down (z direction).