I recently had a shower replaced by a local contractor. He installed a PVC pan to my old copper drain. Needless to say it leaks. He doesn't understand why? I believe that the correct way should have been to cut the copper drain and install a PVC pipe to the shower. Can someone help explain what is wrong and how to best fix it?

Yes you'd need to cut the copper drain off and replace it with a pvc and stub up into the shower pan and then cut it off , we use a tool the cut from the inside of the pipe out but cut this and install the drain,

Also any post you have of plumming be sure to post in that forum or ask speedball,