My water main broke from the 45 degree angle elbow it has on it going down in my yard. The fitting just blows off when I reattached it. It's 40 degrees outside and the glue has had 6 hours of cure time. The main issue is the angle it is just slightly off. We are about to try a 22-1/2 degree angle fitting. Do I need to dig it completely out to do this or just reattempt it with a better angle? What would a pro do?
PVC pipe is actually welded together by the glue. The two mating surfaces softened by the glue actually intermingle and fuse. When the glue cures the pipe and fitting become a single PVC piece.
Temperature, among other factors, effect the time it takes for the bond to reach full strength. If I remember correctly the glue directions state (paraphrase): "let the joint cure undisturbed for 12(?) hours. Reaches full strength in 24 hours".
I've found the joints hold best when using a PVC primer with the glue. Also use a "full bodied-type" glue also labeled as a "hot" glue. It preforms better when the pipe is leaking water and in cooler climates.
As far as your joint being under stress due to a wrong trench angle shave the trench wall to allow the pipe and fitting to un-bend. This isn't as important as ensuring that the mating pieces are clean, that a full coating of glue is applied to the entire mating surfaces of both parts and that the pieces are pushed together fully and then held tightly for several seconds.
A trick I have used in cold weather for gluing pvc is to wrap the joint in a heating blanket while it cures. Of course if you believe the joint is stressed you should relieve this first by cleaning up the trench angle. This will prevent you having to do this again in a few months. Also, don't get crazy with extra fittings trying to fix an alignment mistake. Extra unnecessary bends in your main line will drop the water pressure in for your entire house.