Compressed Air Lines

[Bruce Kohl]

I'm going to install air lines in my shop leading from my compressor to various points in the shop where I'll install quick connect fittings. I am planning on using 1/2" copper pipe with sweated fittings for the lines. I'm not using any high air volume tools, so the 1/2" size should be fine. The maximum pressure from the compressor will be around 150 psi. I know not to use PVC for the air lines for safety reasons.

My question is can I use Grade M copper pipe for the lines instead of Grade L? Around here the Grade M is considerably cheaper than Grade L, although the walls are thinner. Does anyone here have any experience installing copper pipes for air lines?

Thanks for any help.

[Bruce Page]

I ran ¾” L in my shop. Both L & M will work. The extra 40% wall thickness of the ½” L gives more peace of mind and the extra cost will soon be forgotten.

[Ken Fitzgerald]

I'm in the thicker wall camp for the same reason as Bruce.

Are you planning on installing any type of drain for water that accumulates?

[Bruce Kohl]

Ken - I thought I'd put in a ball value below each quick connect fixture so that I could periodically drain any water that accumulates in the lines. The lines will be installed on the wall above the compressor height, and will be slightly angled down to the drops for the quick connect fixtures. Is this adequate?

Water in a compressor or the air lines is not too much of a problem here in New Mexico as the air is so dry, but you still need to periodically drain the compressor tank and lines. I have a water filter on the outlet to the compressor and only open the drain value every few months. Even with that I rarely get any water accumulation. Ditto with the tank drain as not much water accumulates in the tank.

Thanks for your advice,
Bruce

[Bruce Kohl]

Bruce - Why 3/4" pipe in your shop? The ID of 1/2" copper is much greater than the ID of even 3/8" hose, so it seems that the 1/2" would handle the volume of air of most home shop compressors.

Also, is there any danger (like with PVC) of using the M grade copper in the event of a failure? It seems that all the copper would do is split rather than shatter like PVC might.

I see you're in Albuquerque. I'm a fellow New Mexican from up north in Santa Fe.

Thanks for the advice,
Bruce

[John C Bush]

A plumber friend of mone used Pex for his air supply lines. He said hose and fitings are rated for 100+psi for water. I prefer copper.

[Matt Meiser]

I ran 3/4 for my main trunk and 1/2 for drops, whatever Lowes had because I didn't know there were different grades at the time. 10 years later no regrets. I ran a new drop about 4-5 years ago and did it with PEX, again no regrets. PEX is not rated for air (there is a version with an aluminum core that is) but since it does't shatter like PVC I felt safe enough and the expense was low if it was a failure.

[Chris Parks]

There is some really nice "plastic" air lines with no fuss joiners that can be used and pulled apart with minimal tools, much better than copper any day of the week. How could you go past this http://www.youtube.com/watch?v=CtVHQPH8nMI

[Mike Cutler]

Bruce

The larger the diameter of the piping, the thicker the walls would need to be for a given equal pressure rating. However, the burst pressure of either M, or L copper pipe is well above your intended purpose. The working pressure of Type M in 1/2", or 3/4" is close to 500psi at <100 degrees F.
3/4" lines are used for pressure drop mitigation. While the orifice restriction of most "Home Owner" type tools is something <3/8", the CFM, and pressure drops across a system can have a potential effect. If you were to open up a 3/8" diameter orifice in a small system, you would quickly exceed the capacity of the system as a whole to keep up. So while the top may have a 3/8" fitting on attached, it can use a significant amount of air depending on it's internal construction. 3/4" pipe would keep up longer than 1/2" pipe, for the same compressor rating. However the compressor capacity will ultimately be the over riding factor.
Bruce Page is a machinist by trade, so it doesn't surprise me that he has 3/4" lines. His "homework" could be quite a bit of different than typical use.
None the less, 1/2" Type M will probably meet all of your needs, safely, excluding a large bead blaster.

[Jim Andrew]

I bought a Rapidair kit, 1/2", and installed it in my shop. Needed 1 extra T, as the system is designed for the compressor to be in the middle of the system. You get a bunch of L's and one T. You use pex brackets to attach it to the wall. The system works great. You use a short air hose to attach your air compressor to the system. One advantage it has over copper is that the line is flexible, the pipe comes in a roll, and you can bend it around a corner.

[Chris Parks]

The big advantage of using a larger than needed line is air speed. The larger the air line the lower the air speed and the lower the air speed the less moisture that the air will carry out of the compressor. I would not install anything less than 3/4 and one inch would be a better especially if spraying. The advantages of the new poly lines are such that copper should not even be on the horizon.

[Steve Rozmiarek]

I'm surprised no one is recommending black pipe. It's been the standard for a very long time, supports itself, and is simple. Spark, abrasion, damage resistant, unlike plastic, and not very expensive. The newer plastics are good enough now, but still have some drawbacks. Air lines move too, vibrations from the compressor, tools, temps, etc all shake the lines a bit. I wouldn't use copper because it doesn't resist this well. Check out the auto shop air systems next time you are in there if you want to see a system that holds up well.

That all being said, it's a woodshop, a 1/4" plastic spring coil hose is adequate for most of the stuff we do in them.

[Bruce Page]

Bruce, I checked my lines this morning and they are actually 5/8 OD, not 3/4. I have no real reason other that a Tim Taylor, bigger is better mentality.

Did you get any snow yesterday?

[Peter Kelly]

I'm surprised no one is recommending black pipe. It's been the standard for a very long time, supports itself, and is simple. Spark, abrasion, damage resistant, unlike plastic, and not very expensive. The newer plastics are good enough now, but still have some drawbacks. Air lines move too, vibrations from the compressor, tools, temps, etc all shake the lines a bit. I wouldn't use copper because it doesn't resist this well. Check out the auto shop air systems next time you are in there if you want to see a system that holds up well.

That all being said, it's a woodshop, a 1/4" plastic spring coil hose is adequate for most of the stuff we do in them.

I did iron pipe air lines years ago and it worked out really well, was up to building code, self supporting etc. The only caveats I'd say is to not buy anything from the big box stores. Chinese-made nipples, pipe and fittings often have crooked poorly machined threads that don't mate correctly which will lead to leaks everywhere.

[Jerome Stanek]

Also with black pipe you can go a lot bigger for the money and bigger means more air storage.