Weird question

Hi--I've been here before over the years but haven't really established myself. I have been a kitchen and bath remodeler for several years after mostly building new construction. I've been around an awful lot of "interesting" plumbing situations, to say the least, but I have never seen anything this unusual.

Situation: replacing a sink/disposal. Problem: 1 1/2" pvc threads on new trap simply DO NOT mate up with threads on old elbow coming off the y pipe. I have looked at this from every angle, and played with all kinds of possibilities, but it comes down to this--did PVC manufacturers actually make a change within the last 25 or so years, and make these things slightly (and boy, do I mean slightly) different? the new part matches perfectly to threads on other fittings I have, and the old one does not. The new pieces are definitely wider, meaning stronger, than they used to be.

I'm hoping all the old hats will chime in and tell me this is common knowledge and the parts are available, but thought this to be so strange since the pieces look Identical, and everything is right, except they won't work.

Help!

Thanks!

shoot. didn't see that this got posted into toilet forum. Maybe someone can move it over?

threads

I do not know what you are working with, or trying to do, but the threads are the same as they have been for at least a century, so you have to give us a picture of what you are having problems with. Unless you are referring to the union nut on the outlet of the trap. That nut is NOT a standard part and can have any thread the manufacturer decided to use. Sometimes they make them unique so you CANNOT mix some other brand of trap with theirs.

You simply do not know what your doing. Stop playing plumber and pay to have ot done right. Just think, you gt on-line, post questions, check back, god only knows how many parts you have already bought, and whatever. Im not bustin your balls, Im telling you how it is. Pay a little now or a LOT later.