When using threaded pipe you rely on tightening the pipe threads to seal the joint. If you use the PTFE paste (joint compound) when assembling the black iron then you most likely won't have a problem with leaking. The teflon tape gets shredded by black iron threads so it doesn't tend to work as well. Shredded tape equals increased friction.
If you use black iron, install a union fitting when coming back down the wall so that if you do have a leak, you can just undo it at the union and work from there instead of taking everything downstream back apart.
Another positive with black iron is that the increased mass in the pipe acts like a condenser / heat sink and stays cooler longer. Use at least 3/4 thoough as this will keep pressure/volume drop low over distance.
Copper Pipe and Sharkbite
I used 1" Copper with Sharkbite Fittings. Its expensive, but these fittings just push on and pull off (with a release tool) and can be removed anytime and used over and over again to make modifications in the system. All my services exit the main pipe just below ceiling level by going up, then dropping horizontal down to the floor with a drain valve. Sharkbite fittings allow you to rotate the direction of the pipe in any direction at any time. From this horizoneal line, the service makes an exit vertically to the outlet. I run about 60 feet of pipe before my first filter. By the time the air gets to the filter, its very dry. I also installed an automatic drain valve on the bottom of my compressor which can be set to automatically blow down and exhaust at intervals I choose. If I want it to exhaust every five minutes for 10 seconds, thats where I program it. The vent pipe for this exhaust is routed outside to an underground baffle where its kept quiet and the moisture and compresor oil are confined. Expensive, yes. The heavier copper pipe is very expensive. The one inch sharkbite fittings are even more expensive. This was a one time expense which has really helped provide a dry air source before the air ever enters a filter. That cuts down on the cost of decissant which can be an issue off you are not planning a system to cool down and dry your air before it gets to the filter. If you want to add a service or change the location of an existing service, you just rotate or change out the Sharkbite fittings. At 100 PSI, my supply lines loose about 3 psi in 8 hours. I believe threaded steel pipe would be my next choice and definitely less expensive than copper.
How many feet of pipe in your system? Do you think it would be less expensive to use steel pipe and a $1500 refrigeration unit to remove the moisture?
Originally Posted by Outlaw56