The cap on a 1" Plastic cap on a 1" water line released when the ball valve was opened a quarter of a turn. It is my understanding that the end cap was a plastic cap that threaded on the end of the pipe. The system had been previously tested at 150 psi. Are the plastic end caps sufficient for the amount of pressure a 1" hot water line would produce or should the contractor have used another product? Was the contractor negligent or is it common practice to use the threaded plastic end caps for such a large water line in a commercial; building?

Is it PVC cap ?

We could use more details. Type of threaded pipe the cap was on. Copper, plastic or galvanized? Describe the fitting the cap threaded into. Give us something we can work with here! Cheers,Tom