Plastic air line pipe is the new way and safest. NO Copper or PVC. I ran 1/2 steel water pipe. 30 years ago still works great. 110 lbs in lines consistant. Remember always run up hill from the compressor so moisture drains back to the compressor. Put at least a 12 inch nipple under the fitting at the bottom of the drop and a drain at the bottom of nipple. We also have a automatic electric water drain in the tank that activates every hour to keep water out of the tank. we still get water at the drops and drain them when ever you plug in a hose. Even though we have a water separator at the compressor. We us a toilet paper filter for painting. They are the best. New roll every paint job.
In the back ground you can see the toilet paper filter and the drop with drain on the other picture. The rust mark on the wall is from the drain. Copper and PVC are not safe. I have seen copper split but not near as dangerous as PVC.
View attachment 1715406315
View attachment 1715406317