Quote Originally Posted by cffisher View Post
From what I found those rateings are for 7"od and .540 wall thickness but I've been wrong before. I still wouldn't use black pipe for air compressor
Don't think so.
Wrought Steel Pipes - Bursting Pressure

Black pipe has been used for air line for decades. I would use it over PVC for sure. I've seen PVC shatter under pressure. makes good shrapnel.