When I flush the toilet there is a dripping noise but the pipe under the toilet is visible downstairs and there is no leak. This started after a reno in the adjacent room but the only pipe in that wall the pipe for taking in air that goes upto the roof and the water supply. The only thing that makes sense to me is that the air pipe is tighter in that wall and due to expansion from the room temp water, it is making a drip sounding creak. Does this sound likely or should I consider ripping back open the wall? Note its behind tiles/ cabinets