I have a half inch cold water copper line connected to a half inch PVC pipe with the threaded (male) pvc adapter...about after a couple of months it will start to drip. I use white teflon tape but it seems to over time loosen in some way...As you know you can only snug these fittings so tight without cracking the PVC.....but I repair it, and its damn hard to get to too..and about 2 months later the wood around it shows me its dripping...I have fixed it 3 times so far and today I am repairing again..I am almost at a point of teearing out all the PVC in that line and doing straight copper.
Any suggestions..BTW: I jsut had another copper to PVC with the same issue but it was simple to get to and repair...