Have a pump inlet that I have put a PVC male threaded adapter to PVC pipe, then an elbow, etc for inlet pipe. Last year I had the threaded end shrink and deform and come out of the pump body. It had a fair amount of weight of the pipe on it so put in a support for the pipe and replaced the fittings. Just had the new one pop out after a couple months. The end of the pipe isn't distorted much - just an increased taper on the threads. Seems very strange. Should I try to find schedule 80 fittings? Any other ideas of what is going on or how to resolve it? I know plastics can flow over time but this is more than I have seen before. I will try to post a pic in a bit.