Adding a Y to existing underground sewer main

I'm adding a room to my house and want to tie a new 3" waste to existing underground 4" sewer main using a Y fitting. I've been told that I can't use stainless steel band sleave on an underground application. Is this correct? Any ideas on how I make this connection?

Thanks,
Scotty

Codes vary on this subject. I've heard that in some places you can use the ss banded couplings (such as proflex) underground. Here where I am however, they are only approved for above ground installations while Ferncos are approved for underground. Check with your local plumbing authority as to what are the correct and approved fittings for your application.

Good luck

connectors

Here, Fernco couplings are not allowed anywhere inside the building, but banded No-Hub couplings are okay. In some areas, and yours may be one, MG couplings are required underground inside the building.