I need to add a utility sink and the drain would connect directly into my main stack (see attached picture). Is it possible to add a connection to the main cast iron stack, without cutting out a section and adding a new fitting? Basically, I am suggesting cutting a hole in the side if the cast iron stack and adding a saddle Wye (see picture)my stack as it is now.
My understanding is that saddle wyes are prohibited under most codes, but you should check with your local jurisdiction to be sure.
The usual way is to support the pipe top and bottom, cut out a section, and then put in the new wye with hubless rubber connectors.
I've included a picture of the stack below. After more research, and the help given here, tt is my intention to remove enough of the the stack to insert a 3" PVC wye, using a two short pieces of PVC, glued to the wye, and using two Fernco no hub couplings.