I'm replacing the drain plumbing from my bathroom sink, and there is currently a 1-1/4" male threaded PVC fitting coming from the wall, which I assume is a trap adapter that was installed at some point in the past. I have the nut from it and understand it should tightly clamp around a new piece of pipe, but I can't seem to make it work. There was no gasket there - should there be one? How do I go about attaching the plumbing to this threaded fitting? Thanks in advance for any advice you can provide!!
The fitting you show inthe picture is probably a "desanco" fitting. A tail piece or J bend is slipped into the fitting and a gasket and jam nut seal the joint. This J bend is usually part of a P trap assembly. If in doubt, go to a big box store, show them a picture and they can show you what you need.