I am using the black pipe as well. I was originally thinking about using galvanized, but a good friend of mine who is in the propane business told me that they have run into issues where the system has been plugged up by little chunks breaking off and boogering up the valves/regulators. I thought about the rust as well, but it seems like the filter (especially the one you have) ought to be able to block those particles. the rust is not like the water.........vaporized in the air. They are physical particles that the filter ought to be able to trap. You mentioned that you built a loop of pipe. Is it literally a loop or just a long run from the compressor to your connection point? Thanks and glad to hear that it worked out for you. L8r
Jim