Received my horizontal nipples in the mail yesterday. As I have seen on google, i attempted to install them in PVC pipe. No luck. everytime i tried they would just pop out. I was using 1" PVC. What is the trick? I'm thinking about putting t joints and fitting them with reducing bushings that have 3/8 thread on them to screw the nipples in. http://www.tractorsupply.com/en/store/green-leaf-nylon-reducer-bushing-1-2-in-mpt-x-3-8-in-fpt What have you do to make them work.