If you are careful you can reuse the fitting.
Maybe this is obvious to some, but I want to be sure to avoid headaches in the future...
I want to replace a valve in a PEX run, and plan on removing the existing valve by removing the PEX by cutting the crimp ring off one side of a brass elbow like the one pictured.
I would then crimp new PEX pipe onto side of the elbow from which I cut the ring.
Will this work, or am I inviting trouble by reusing the elbow?
You have lots of room to cut the ring off without damaging the elbow, if the elbow still has all it's barbs on it you're good to go.
Some PEX kits come with a crimp ring remover that does what you want to.
Licensed residential and commercial plumber