[NightHawkInLight] a.k.a. [Ben] recently built an awesome high power air cannon out of PVC pipe. PVC air cannons ... been replaced with a valve from a sprinkler system, giving this high power ...

Either the sprinkler head has broken or, more likely, the riser has broken. The riser connects the PVC pipe to the sprinkler head. Risers are short lengths of pipe that have male threads on each end.

plastic polymer pipes is for plumbing, but they can also be employed for rainwater collection and distribution, fire sprinkler systems, cable installation, various other PVC DIY projects ...