I heard of using a Vac on the line and sucking in cleaner and then glue. If it is a hub that is leaking try drilling a hole in line with leak, make sure you go through hub only not the pipe, and use a vac and suck the cleaner in the leak a couple times and then suck it dry and do the same with clue. You can also cut out pipe and use 2 nohub bands and replace the leaky fitting and new pipe with a new one.