Recently a friend came by as I was doing some work on my sprinkler system and noted that I was using both the purple primer and the clear "glue". He Is now a bit concerned as he says he thought the 'purple stuff' was a glue and did put together his own sytem at his home using only it. He says he did before burying most joints put them under presure to check the bond for leaks, all seemed fine, and has seen no leaks since then. Does he have a real problem?
I once saw a DIY system that had lots of pinhole leaks on the interior PVC plumbing joints, that the homeowner tried to patch with epoxy putty. He told me that his friend "had assured him that there was no need for primer" when assembling PVC. Too bad his friend was an electrician and not a plumber.
PVC pipe and their fittings are designed for a snug fit, and using primer helps make that snug fit even tighter. So I can believe that he managed to put everything together, did a quick pressure test, and everything was fine. But without glue, over time, the stress the water pressure and the turning the water on and off WILL cause the pipes to move, loosen, and leak.
Though it begs the question how a DIY did a whole system without ever needing to ask any questions or read any instructions that would have clued him in that "PRIMER" is NOT "GLUE".
I've seen pipe put together with just primer that you just can't get apart. He may have mistaken that for a glued joint. As a plumber I've seen this happen a time or two (people in haste primer a joint but forget to glue). Of course they eventually leak - thats how we discover that they were not glued in the first place.
Another thought crossed my mind -- the neighbor isn't confusing purple primer for blue glue is he?