Black pipe or galvanized for shop air lines?

blackdog2086 · Aug 3, 2014

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 · Aug 3, 2014

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 · Aug 3, 2014

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 · Aug 3, 2014

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 · Aug 3, 2014

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 · Aug 3, 2014

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 · Aug 3, 2014

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 · Aug 3, 2014

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 · Aug 3, 2014

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 · Aug 3, 2014

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

franklin2 · Aug 3, 2014

You can run PVC with water lines, if it breaks you will get sprayed but that's about it. Using it with compressed air(or any gas) is different, when it breaks it's like a big spring behind it and throws shrapnel all over the place. You could use it if there is some sort of shield around it, but why go to all that trouble.

I have worked in factories for years and we always use black pipe. You will always get some water in the piping, and yes that will create rust. But there are ways to minimize it.

1. Your trunk line piping should be slanted toward the compressor. Ours fell toward the storage tank, but I am assuming your setup will have the tank and the compressor built together. Any water in the lines should run back to the tank where it can be emptied out on a regular basis. Low spots in the piping are where you get water puddling in the pipe, and that causes problems.

2. When you tap off the trunk line, you should point the tee up. I know it will be more work and more fittings, but that keeps the water in the trunk line migrating back to the tank instead of your drop. Come off the top, and using fittings to work it around the trunk line and down to the work area.

3. Like was mentioned, at the bottom of the drop don't use a elbow, use a tee with a valve pointing down where you can drain the drop if you need to.

Do all the above and use a filter with a sediment bowl, and you should not have any problems.

BHD · Aug 3, 2014

I used gallivanted, mostly because of the ease to getting it,

I basically followed the guide posted below, and have very little water in the lines. the traps do work, and sloping he lines help a lot,

Deere Dude · Aug 3, 2014

CPVC is the cheapest route and I have it in my house. If it wasn't so hard to change it I would pull every stinkin' bit of it out and put in copper or PEX. It is brittle and a bump can break it. I dropped a bottle of shampoo and it hit the tub faucet and it snapped it off. To finish showering I had to get on my hands and knees. I was replacing a valve in my kitchen, held back when loosening, but it still snapped. There is another one broke. If you bump an air line with compressed air it could be nasty.
In the factory I worked at as a pipe-fitter, all air was in black pipe. In a system without an air dryer I would go with copper because of an internal rust possibility, it is durable and it looks nice and it's easy to install. I installed 3/4" copper with 1/2" drops in my unheated pole building in Wisconsin and worked fine.
I used it for 5 years then decided it is just as easy to hook a air hose to my compressor and run from that.

EddieWalker · Aug 3, 2014

I put a T on my compressor and have two hundred foot hoses for outside and one fifty foot hose for inside my shop. I roll up the hoses and keep them and garden hose metal holders attached to the wall. I got to thinking about running lines and can't justify the expense or time when it doesn't accomplish anything other then giving me another location for the hose to connect to. The hose will still be running across the floor of my shop and it doesn't matter where it's attached to.

Eddie

kennyd · Aug 3, 2014

Copper for me in my shop and basement.

PVC or CPVC is just plain dangerous.

Here is just one documented accident: https://www.osha.gov/dts/hib/hib_data/hib19880520.html

kennyd · Aug 3, 2014

Copper for me in my basement shop and garage.

PVC or CPVC is just plain dangerous.

Here is just one documented accident: https://www.osha.gov/dts/hib/hib_data/hib19880520.html

Gary Fowler · Aug 3, 2014

EddieWalker said:
I put a T on my compressor and have two hundred foot hoses for outside and one fifty foot hose for inside my shop. I roll up the hoses and keep them and garden hose metal holders attached to the wall. I got to thinking about running lines and can't justify the expense or time when it doesn't accomplish anything other then giving me another location for the hose to connect to. The hose will still be running across the floor of my shop and it doesn't matter where it's attached to.

Eddie

I agree totally with Eddie. I thought about plumbing my shop after reading several post on TBN but then thought that you still need hoses at each drop so it is a waist of time. I can also move my compressor if need be to anywhere in the shop or even outside to minimize the amount of hoses needed. I have a 3 sections of 50 feet each and can get about anywhere I need to go with hoses and with the hose rack I built on the compressor, it stays neat and out of the way all the time. It only takes a minute to roll it back up when finished. Unless you have a huge shop with multiple users at the same time, piping in a compressor is a total waste of money.

jejeosborne · Aug 3, 2014

In today's world, I would look into PEX as well. It is flexible unlike pvc making installation quick with fewer fitting to possibly leak. When I built my home I used Kitec which has a layer of aluminum sandwiched between the plastic that when bent, it stays. Copper is so expensive and inferior for water lines today.

FredH · Aug 3, 2014

In line with Eddie and Gary , I should note that although I used Black Steel , It was to simply go from Compressor to regulator , ( maybe 18" total length ) . From there , It tee's With a 3/4" quick coupler for my big hose on one end . Then on other end it connects to a rubber 1/2" that goes up the wall to my 100' hose reel . 100' of 1/2" rubber hose on reel plus another 50' of extra coiled up hose hanging on wall if needed .

I found for my uses that utilizing the hose reel was the easiest and cleanest option and the most versatile for both inside or outside situations .

Fred H.