Black pipe or galvanized for shop air lines?

[blackdog2086]

It is my "intent" (key word) to plumb my pole barn for air on my next trip home. I've read a number of posts here, and know that PVC is not the way to go, so metal pipe is definitely what I'll be using. My question is, should I be using black pipe or galvanized for the lines? I won't be running an oil system, as I'll be occasionally painting, and I won't be using tools enough that manually oiling them would be a problem.

I'll be installing a water filter and drops with ball valves throughout the barn. Is the small amount of water in the lines enough of an issue that it even matters as far as potential rust is concerned? I know a lot of this is opinion based, but I've gotten a lot of good information from this site, and am definitely willing to listen to what anyone has to say.

 

[FredH]

I used black steel . My though was since that is what is used around here for natural gas from meter into houses , it would be good enough for my shop air lines . :confused3:

Fred H.

 

[dms0519]

I used 3/4 pvc when I built shop 16 years ago.Run 175 lbs air pressure constantly as compressor is always on and have yet to low an airline.Air is used everyday without a problem.lots cheaper and easier to work with,

 

[pmsmechanic]

Some of my friends have used pvc with no problems and I have 3/4" and 1/2" copper at 175 psi. Both work fine for air lines and are far cheaper and easier to work with. But if you want to use steel it will work too. Just make sure that you add some traps for the rust and water.

 

[the old grind]

I suggest that PEX might work better than PVC (oxygen barrier-type), but you'd want to use 3/4" vs 1/2" to minimize flow restriction, esp if you were to use poly vs brass fittings. Galvanized is not code for NG in our area even at the low pressure compared to water. Don't know if that's because plating may flake off & cause issues or the possibility of chemical interaction between zinc & gas or the mercaptan odorant.

Condensation will likely concentrate in the tank vs lines. Of course, installing drip Ts at each drop is wise, but having installed valves on them vs caps I've yet to release a significant amount of moisture from those used most frequently. Moisture traps must be monitored and filters changed on a somewhat regular basis, esp on the drop you paint from.

Refrigerated air dryers are a luxury few can justify unless using copious amounts of air such as with a blast cabinet. FLRs are cheap and perhaps best placed at drops where power tools demand the lube. No sense oiling a whole branch. Doubling drop outlets can have advantages too, say one with FLR for tools & one w/o at higher pressure for that blast you'd use to clean something off. This may make more sense if your system is charged by a 2-stage vs SS pump and at higher pressure (>100 PSI, etc). btw: most power tools are intended to be operated at 90 PSI so they work ok between pumping cycles.

Not much to gain by sizing trunks much bigger than 3/4". Total system volume will supplement tank capacity and moderate pressure spikes, if that were perceived as a problem. Re-purposing components may not be worth the bucks saved. Brass valves have nearly doubled in price in 5 years, and tho' gates are nice, ball-cocks are the way to go. Make sure all are 'full open' type.Separate components (FLR, etc) that have service intervals. Plumbers use unions to ease maintenance/upgrades later but can be temporary trouble spots if doing them in a rush.

A main shut at the tank is the first place to put one for obvious reasons. Adding a gauge beyond it allows you to recognize downstream leaks. Buy or mix 'bubble stuff' to spot them during installation and later. I would use black iron period, but that's just me.
Don't cheap-out on something you want to last if you want to do it once and be done with it!

 

[Buckgnarly]

No way I would run PVC, hack at best. If you really want to do it right the first time and forever, go with copper. I would really be worried about rust if you plan on this for mainly painting, especially flaking.

 

[KennyG]

Either galvanized or black would work fine. Seems like black is usually used. As several have noted DO NOT USE PVC. People get by with it for years but after aging or when you drop something heavy on it it will explode and cause scrapnel. It is expressly forbidden by building code for compressed gas service.

 

[chim]

Not sure if it would be an issue wit air, but black pipe is specified for fuel piping because of the potential for tiny pieces of the zinc getting in the fuel and messing things up.

 

[the old grind]

I would caution against using copper if in an unheated building. Want to know why the hot water pipe freezes before the cold one? Metalworkers do. During normal use, expansion/contraction over the wider temperature range 'work hardens' the metal (google that term) & it becomes brittle, has less 'give' at the onset of freeze and splits. Copper is ductile, but water pipe is not pure copper and even that has its limitations

btw: Same applies to brass, so when you bury ammo in the yard make sure it's below the frost line. Split necks and case head separations can lead to cycling issues, and you could be zombie food before your MREs run out when you-know-what happens, & you know it will or there wouldn't be several $k of ordnance under the petunias.

 

[Bill Hoffman]

Used black pipe for my first shop installation, bad move. Internal rust everywhere.
Ruined filters, regulators, an air ratchet and air sander. Replaced with 1" copper tubing
years ago, NO problems whatsoever. Do it right the first time, you will only regret
the initial price.

Bill