I am changing the location of all the fixtures in my bathroom. This move will put the toilet and sink on the opposite wall from the stack. I was originally planning on running a vent up the wall with the sink and across the ceiling to connect back into the stack, but this was assuming I would be replacing the 85 year old cast iron pipe with PVC so I could easily add a new connection up at the ceiling height. Now I am considering leaving the existing cast iron stack and trying to just reuse the existing connections.
There is already a vent connection on the stack that is above the height of the sink, so if I could get the pipe over to this connection I could reuse it. However, to do so I would have to come up the wall, across the ceiling, and then back down the wall with the stack (so I use the old vent connection that is about 4 feet from the floor). I can't just route the vent horizontally around the edge of the room as there is a window on one wall and a door on the other.
Would this configuration meet code? It seems to me it would work fine since it will always stay above the "overflow height of the tallest fixture". I am in Ohio, the Ohio Plumbing Code is based on the IPC.
║ stack> ║ ║ ║ ╔══════════════╗ ║ ║ ║ <vent ║ ║ ║ ║ ║ ║ ╠══╝ ║ ║ ║ ║ ║ ║ ║ drain> ╠═════════════════╝ ║ ║ ║
EDIT - The drain is 3" and will have a toilet sort of in the middle and a sink at the end (near the vent). The 3" drain may also tie into the tub drain or I could connect the tub to the stack separately (the tub is right next to the stack so I have more options).