[quote author=logans_daddy link=topic=2312.msg25595#msg25595 date=1252354815]
:TWOCENTS i think threaded pieces are less likely to fail than glued. the chemical bond created by pvc cement can break apart over time. ask any plumber. with the exception of a threaded union, a threaded piece can not come undone overtime without the entire pipe its glued to spinning freely and if that happens you have more important problems.
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I don’t agree with this. IF a plumber were to think that, why are ALL of our houses (that use PVC) done with glued PVC joints behind the walls? A threaded joint runs the risk of a mechanical failure for many reasons: Overtightening, under-tightening, too much tape, not enough tape, manufacturing tolerances, etc… A glued joint has been, and always will be the best solution when joining two pieces of PVC. If you prep the end pieces with the correct primer and use the correct solvent, it will not fail. I say correct primer and solvent because if you use Schedule 40 as opposed to Schedule 80, they require a different type of primer and solvent. It works in the same exact way as building an acrylic fish tank or sump, you are chemically modifying the two pieces of PVC and “welding” them together.
Now, that isn’t to say that using a threaded connection in our setups isn’t sufficient. I can’t see where we would get to the PSI that we have in our household systems, unless you were to try to push 1000gpm through 1/2" PVC, even then, there is still no true pressure building up in the pipes, just a lot of back pressure on your pump, which in this case would make the pump fail before a connection of any case, in my opinion.
Sorry for the HJack. However, one question I do have for using PVC is the effect of our high intensity light on schedule 40 pipe. But, I will start a new thread. 