When I installed a compressed-air distribution system in my hangar I was planning on copper lines until I noticed one of the long-respected automotive shops used common 3/4” PVC. I asked the owner of that shop how that worked out for them and how often they’d had to make repairs to it. (I had researched this topic and PVC pipe was specifically forbidden for such systems by respected engineering firms due to physical damaga hazards.)
The shop replied they’d installed the system in 1979 and the only modifications they’d made was when they extended the system into the newer repair-bays in 1985. They’d never had a failure.
What really surprised me was they are running their system at 160 psi.
I only wanted 125 psi.... so I created my system using the same 3/4” pvc and glue. I have almost 225 feet of pipe and almost 40 fittings and 6 manifolds. I completed the system in April 2000 and have never in these 20 years had a failure. (DAMN that went by fast!). Common 3/4” sched. 40 PVC is rated at 480 psi and I feel that running at 1/4 of that rating is sufficiently safe in a private non-commercial operation. YMMV