I was trying to mount a shelf and while drilling holes for the screws, felt some resistance against the drill. Tried to push the drill a bit further, but stopped as I was not sure what the resistance was. Removed some more drywall to see that I had scraped a 45 degree elbow joint on the PVC drain pipe. The scrape looks like its right at the end of the elbow (bell-end?). This looks like a drain pipe draining from the 2nd floor. There is no leak. Can I just put some epoxy on this or am I going to need to do a bigger repair?
