I need some advice. I was installing shelves in a closet and while driving a screw realized from the feel of it that it was not going into a stud but rather a verical PVC waste pipe from the bathroom upstairs ( I remembered the pipe being there after the fact). It is not leaking, but the question is, should I repair it now? I did a search for similar problems but all seemed to recommend a coupler. It is a large pipe (probably 3.5 inch) with no clearance behind the drywall, so I'm not sure how a coupler would work out. As I am not a plumber, just a DIYer, any input would be appreciated. Thanks.