Noticed a water stain in the master bedroom ceiling. Went into the attic to see if I could identify the source, and I could not. The ceiling is pitched and the location of the stain is at the lower end of the ceiling so it is very difficult to get to. I contacted a heating and air co. to see if they could identify the problem. After they inspected the area, they said it is not the duct work. The only other thing near that area is a PVC pipe, which runs from the front side of the roof to the backside. I believe the PVC pipe has something to do with the vents that run out of roof. Any idea what could be causing the water leak?