All fixtures in 1920's 2nd floor bath are stack-vented. Sink curently uses S-trap to floor with about a 7-foot run to stack.
We would like to improve this situation without adding a new vent up though the roof or reventing back to the stack through a wall, which would entail ripping apart the plaster/lathe walls and disturbing the ancient soil stack.
What about a "chicago loop" type thing like people do in kitchen islands, where the new sink's P-trap goes back into the wall and then includes a loop in the wall, as shown, where the top elbow is higher than the water level, and where the drain line back to the stack in increased to 2".
Would this work? Any other ideas? Our town uses the International Plumbing Code rules.