Choosing an Air Line Material

      Shop owners discuss the pros and cons of various metal and plastic tubing materials for compressed-air supply lines. March 20, 2006

I am going to move my compressor from the main floor of my shop to the basement, and I want to run hard lines to stations instead of using the retractable reels I am using now. What is the best thing to use? I have seen iron pipe, copper, PVC and even heavy airline tubing like is used in fish tanks (which looked cool, but the fittings were high priced).

Forum Responses
(Cabinetmaking Forum)
From contributor P:
We ran 3/4" PVC, which is kind of marginal, but inexpensive - if I was to do it over again, it'd probably all be in copper. Some jurisdictions don't like PVC, as it can become brittle over time and shatter, but I haven't had trouble. The plastic tubing you're referring to is probably cross-linked polyethylene, made by Wirsbro and a few other companies. Wirsbro specifically warns against having their tubing exposed to sunlight for any extended period of time, so it wouldn't be a good choice for surface-run lines. Don't know if another PEX company has incorporated UV resistance into their material.

From contributor I:
Go ahead and use copper. That's what I did and it's not really all that expensive. Though in the past I've been in shops that used PVC, I wouldn't do it - if one of these shattered under pressure, the shrapnel could be ugly.

From contributor S:
PVC is the cheapest and most dangerous way to go. As mentioned, not allowed in most areas. In reality, probably not allowed anywhere. Black pipe costs more in both materials and labor to assemble. Add to that the fact that if you have a leak or need to add a drop here or there, it is a pain to disassemble and reassemble everything. Black pipe also has more rust and scaling that occurs in it. Copper is costly but easy to assemble. Never leaks and is very easy to add on to. Worked in shops with all three and in my opinion, copper is the winner, hands down.

From contributor L:
There are several of the aluminum extrusion air systems out there. Great for industries that change a whole lot, but pricey. We used copper - not very expensive, and easy to work with. Easy to change around, too. Check out the system design info that is on the air compressor manufacturers' web sites. Use a loop system to equalize flow to any point. If the basement is at all humid, pipe the intake air in from outside or from a filtered inlet in the shop. Compressors put off a lot of heat; can it get out of the basement?

From contributor R:
Black pipe is the norm, but K and L copper are okay. PVC is against OSHA standards and should be an insurance risk as well.

Chem-aire and a few others make an abs plastic pipe that is rated for air. I recall the PEX suggestion and the manufacturer said it was not rated for air. For some reason, many people do not contact the manufacturer for tech help or verification of material uses.

Drops are supposed to go up, then down. Keeps the water from collecting in them. There are books put out by the compressor companies that show how to properly run airlines. Been to a lot of companies as a machine tech and can't tell you how many shops think you just run airlines any way you want. Those are the shops with moisture problems in the lines. The web is cool, but it still pays to contact a certified pro to verify info.

From contributor S:
I forgot to mention that adding a dryer and filter in-line after compressor is the best investment you can make in an air system, no matter what materials you use.

From contributor M:
Been using PEX for over five years. It is correct that this is not rated for air and the manufacturers will not accept any liability, but it sure does work. Five years and not even a leak, let alone one of those projectiles PVC gives you once or twice a year. I feel putting the money into a quality air dryer has paid more dividends than running my air through a rigid pipe - no more bottles to empty, although a few well-positioned oilers may be needed if you have been running moisture through your equipment for a while. Black pipe and copper work, but what a pain in the butt to modify. You can drop in a new port or branch off of the PEX in minutes, not hours.

From contributor C:
I guess I'm just a cheap slacker, but I draped a bunch of regular rubber air line across the ceiling trusses with drops to air stations at benches and machines. Been okay for 9 years now.

From contributor L:
The disadvantage to rubber hose is the friction losses, but if it works, fine. Copper is really easy to install and modify. Over the years, our shop has undergone many changes and grown in complexity. Now I wish I had started out with a larger piping system. I started with a 3hp compressor, then a 10, then two 10s, now a 25hp screw. Can't plan for everything! One of the best things we did was buy a good-sized refrigerated air drier. No more moisture in the lines. Also have a big coalescing filter that takes out any oil or whatever else comes down the line.

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