In this video, This Old House plumbing and heating expert Richard Trethewey has a quick cure for a creaky pipe.
1. Go into the attic and locate the PVC vent pipe.
2. Check the clearance around the pipe where it passes through the attic floor and the roof.
3. If the floor framing is tight against the side of the pipe, use a compass saw or jab saw to cut away just enough wood to clear the pipe.