More information on the "black pipe" please. I hope to revamp my garage over the next few months.
Black pipe is common ordinary pipe sold at the hardware stores - actually there are two kinds of "common ordinary pipe", Galvanized pipe and Black pipe. Both are iron pipe and rather cheap.
Galvanized pipe is usually silver colored (from the galvanizing coating) and used for plumping water systems. The galvanizing lessens the rusting of the pipe. The disadvantage of galvanized pipe is the the galvanizing coating can flake off inside the pipes.
Black pipe is the same stuff, except that it's not galvanized. Black pipe is used for natural gas lines, where the galvanizing can flake off inside the pipe and cause problems with the burners and such that are using the gas (plugging the passageways). The disadvantage of black pipe is the it will rust quicker than the galvanized pipe. That means that the air line piping that you install in your garage may only last two or three generations instead of four or five. (Seriously, there are old shops and factories built in the '20s that still have the original black pipe installed and doing just fine.)
Iron pipe is that it comes in standard length, with threads on each end. You connect the pipes with couplers and angle joints that screw together. The hassle comes when you need a length that is not standard (i.e. it comes in 2, 4, & 8 ft. lengths and you need a 5 ft. piece). Then you need to have an end of a longer pipe cut off and new threads put on the end. Last time I had to do that it was something like a buck extra to cut and thread the pipe. However, it takes a bit of knowledge/skill/practice to learn how long to make the pipe - you have to account for the amount of threads that "get used up" when screwing the pipes together, which can easily be an inch or two at each end. It really isn't that hard to do, and the lengths probably won't be that critical if you are off an inch or two in the placement of the pipes. The hassle is that you will probably have to make a couple of trips back to the hardware store to get the pipes cut as you figure out how long you need each piece.
For any type of piping, You also should put "traps" in the pipes as you run the lines in the garage. the pipes will condense water inside them, so you want the whole system to run "downhill" to the end. When you add "drops" for the air hoses to attach, you want to "T" the line, with the drop first going up and then down to the hose attachment. This helps to keep the water from flowing into the drops. A the bottom ends of the drops and at the very end of the whole system, you want to have valves that can be opened to let the water drain out of the pipes. Simple ball valves work just fine.
Here is a good like to a diagram showing an "ideal" set up: http://www.tptools.com/StaticText/ai...ng-diagram.pdf
But keep in mind you can go a lot simpler. As I said before, I have a rubber hose running from my compressor to a ceiling mounted hose reel, and another by my garage door for use on the driveway. I keep meaning to do it right, but I didn't figure I would be in the house that long, and I never got around to doing it right - it been this way for 15 years. But the next hose will have it done right. I do however, have a water separator/pressure regulator at the start of my hoses...