Been repairing a system at one of our schools that is only three years old and has already experienced many main line leaks. We're currently working on nine leak areas and in the first four cases each one has been due to gray glue failure. We've also found that all the SCH 80 TOE nipples are screwed into the valves with no Teflon tape... just pipe dope. Goes to show you that unless someone inspects contractors' jobs all the good specifications in the world aren't worth anything. I'm suspecting that at this failure rate, as we've alredy replaced four other leaking tees and also had a leak in the main line under a bus drive, we'll probably end up eventually having to replace every connection on the system.