pex

can pex be used to run air lines in a unheated shop

Some say no, but I have seen it used for that. Not.saying it's correct. KO

Some people do it.

I've seen it done and I've seen the horror stories that say you'll be sliced to ribbons by shards of PEX when it bursts. There are kits available that use a similar product that is made to take higher pressures than PEX that is put together in about the same fashion. Saw one at TSC the other day. Might look into that if it interests you.

Hello Mr. John,
I would look to the manufacturer and see what they say. You can buy airline kits specific to the use of compressed air for a hundred dollars. It may get expensive outfitting a large shop though and I do not know what you are looking to do.

Asking about PEX rather than PVC, you probably know this, but I will state it, please do not use PVC, there will be folks that say they have used PVC for X number of years and it is fine, it is not fine and it will shatter at some point.

A material failure with compressed air is not like a similar failure with a liquid under pressure. Compressed air has a lot of energy stored in it. Rupture in materials containing compressed gas typically occur at the speed of sound and with air, once the rupture occurs, the air continues to expand, releasing energy until it has assumed local atmospheric pressure.

Compressed gasses should be highly respected and many folks do not give it the respect due. Again, you may know all of this and I do not intend to sound preachy, I thought I would throw out at least a reminder. I continuously see on the inter-webs folks stating PVC is good to go for compressed air usage and their ignorance while giving advice is worrisome.

Respectfully,
George

PEX is not certified for compressed gas. There are other products which are, so there's no reason (other than easy availability) to use PEX for air lines.

Go measure the water pressure in your house. It might be around 40 psi. What are most air compressors rated at or capable of? Mine could push 175 psi. For that reason it would be a big no.

OTJ

It has been done.

Haven't heard the horror stories like PVC, as the PEX is a different type material that isn't likely to splinter like PVC if it fails.

This discussion was had here before, as I remember the reasons PEX is not recommended is, it has never been tested and certified for compressed gas (air) use, and the pressure rating is borderline for use with most compressed air systems. There is also the compatibility with different types of compressor oils.

There is a similar product called "Rapidair" that is designed for airline use. It costs a little more than PEX, but is much cheaper and easier than copper or threaded pipe.
Rapidair

One consideration that doesn't get discussed much, and may not have any application to your use-

I have a friend from childhood that is now a fire Chief for a large suburb of Dallas. His dad was a very practical engineer for the moon shots, so this guy grew up around tools and machines. He and I were discussing hazards at shop fires, and what a shop owner could do to make fighting a fire safer. In a shop fire, there is often a stage of the fire where firefighters can enter the structure, though the heat is intense. Under these circumstance, a fully charged air receiver can serve as a tremendous accelerator should a thermoplastic line fail. The hazard to the firefighters is considerable in such a case. Evidently it is common enough that he puts it on his list of things to ask when they are doing routine inspections, and inform the owner in case they want to address it. Just my 2c.

The PEX I used in the shop floor is not rated high enough for my air supply, and the temperature rating is not high enough either.

I do not believe PEX shatters like PVC.

I used copper in my 3500' shop. I have 2 drops and about 100' of pipe. In the scheme of things it was one of the cheaper projects involved. I ran it myself and had about $250 in material.

I did use pex for the water lines and although functional it looks like crap. Not nearly as straight and true as the copper water lines or electrical conduit.

Go copper,galvanized, or one of the flex line systems rated for compressed air.

I use pex in my shop at 165 psi with no leaks or problems. Pex is dirt cheap those Rapid Air fittings are EXPENSIVE.

The tank itself is the major hazard in a fire. Huge amount of energy stored in one.

(quoted from post at 21:46:56 01/08/17) I do not believe PEX shatters like PVC.

Click to expand...

I just said I heard the horror stories. I doubt PEX actually shatters in normal weather. But cars also don't burst into flame like on V and ammunition doesn't "shoot" the bullet when burnt. Still, you'll hear dozens of people say it happens all the time.

I never thought of the fire accelerant angle. Lots of compressors are plumbed with a rubber hydraulic hose from the unit to the trunk line for vibration/noise.