I had a shop that I plumbed in copper and one with black pipe. Based on
my experience and what I have read about 'pro' installations, black pipe
is preferred for its strength and its heat absorbing ability.
The advantage of the black pipe over other mediums (rubber, pvc, etc) is
that it serves as an excellent heat sink for the hot air coming out of
the compressor. Water vapor in the hot air condenses on the cooler
pipe, resulting in drier air at the outlet.
If you put the pipe in correctly, the air 'outlets' should come out of
the top of the pipe. The water drains should come from the bottom. It's
a pain to put it in with the risers for each outlet but works wonders in
reducing moisture in the outlet line.
See the pipe diagram at
I plumbed my shop according to this plan and I have had no trouble with
moisture in my output lines. I also have an automatic drain on the
I added two items to the power switch. One is an hour meter that helps
me to remember when to change the oil in the compressor. The other is a
strobe that flashes all the time power is on to the compressor. The
flashing light reminds me to turn it off before I leave the shop. I
once had a line break and found the compressor had been running all
weekend. I now turn it off when I leave my shop.