I am remodeling my kitchen. Upon knocking out half of a wall, I disovered a galvanized vent stack going up to a 90* elbow just above the soffit header. My question is this: since I am removing the wall behind the sink, do I really have to replace the vent stack here? There was a cast tee that the waste pipe connected to, water down, air up. But now that the wall isn't there to conceal the stack pipe, do I really have to replace it? Can I just use a wye at the wall and plug the open end that looks up? This is really bugging me because I'll have to cut out 2" holes in the remaining studs which has proven to be next to impossible, not only that but I'll have to run it 6' to the main wall, go up 5' there, back 6' then up to the 90 that's in the ceiling.