Does anyone know the best way to support this stack? I'm going to add another line for a new bathroom. I'm assuming it needs to be supported below the wye. I'd also be interested in where I could find the proper supports for something like this.
The best way would probably be to get a cast iron riser clamp from a plumbing supply store, place it beneath the wye and suspend the clamp from the joists above with steel tape. Or, you could try wrapping the steel tape around the wye and attaching it to the joists. This would probably work, but it might look a little sloppy.