Norman, thank you so much for your question. Without having a better idea of how the vent pipe makes it to the roof (straight up or bends while making its way up) I can not accurately advise you on th ... read more
The BEST way would be infrared image testing. Only top-tier roofing companies will have them, so may be hard to locate in rural areas. However, the technology is getting older, and the cameras that we ... read more