Using pex for air lines

Gary from Muleshoe

Well-known Member
Anyone ever use pex for air lines in a work shop? Been thinking about it but not sure if it will hold up under high pressure, say 150 psi max.
 
harbor freight and other box store and other places have a flexable air line not too expensive, can get the fittings too. dont know if it is pex.
 
I found some specifications for PEX, 160 PSI @ 70 degrees, goes down from there as temp goes up, and I do not know about the crimp fittings.

I think it may be more trouble than it is worth.
 
PEX is not approved for compressed gas. The issue is not whether it can hold the pressure but rather how it behaves when it breaks.
 
I used regular old cheap air line from harbor freight. I took one end off of it and pushed it through some cheap 3/4" PVC so it was easy to strap in place and hold shape. At the corners I just discontinued the PVC and let the hose form the corner. It ended up much cheaper than any other way and the air hose is rated for air pressure.
 
Looking at the "official" PEX websites, I'm not finding any ratings for compressed air. There is an aluminum lined PEX product for gasses, but it is expensive and probably lower pressure than you are wanting to run.

I did find this on a forum, supposedly an email from the factory when asked about compressed air:



"Air is routinely used for pressure testing PEX plumbing systems, and we use it here to distribute the air for our air compressor, so I would say that it should not be a problem for you to do that."

Then I asked about exposure to fluorescent lights in my shop. And his reply was:
"For best results, you will most likely need to cover it. PEX should not be exposed to direct UV light for more than 30 days. I will say, however, that the PEX we are using (for water and air) is exposed to direct fluorescent light and indirect sunlight and is performing well. Still, the recommendation is that it not be exposed to UV light."



My concerns would be that at 150 PSI, you are slightly over the limit at 73F. At 180F the pressure drops to 100PSI. Now, there is probably a large safety factor built into the rating, so odds of it actually failing would be small unless something were to cause the temperature to go beyond the norm, like connecting too close to the compressor or installing near a heat source.

Another concern would be the "droop" factor. It will be near impossible to support the line in such a manner to direct condensation back to the tank or to drain drops. Buying the "sticks" is one way to make straight runs easier than dealing with the unruly rolls. One solution would be to run inside PVC as a conduit. That would provide support and UV protection.

So, for home work shop use, my opinion, it would be doable. Do you really need 150 PSI? That sounds a little high, most run around 100 and are sufficient for most applications.
 
Northern Tool has plastic air line. You can get it in kits or buy bulk. I have had good service from it in my shop. Oh, there is no need for 150 psi, turn it down either with a pressure switch adjustment or regulator. I use a regulator so the compressor doesn't make the line pressure vary.
 
I haven't priced it lately , but the black plastic hose they use on truck air brake lines used to be really inexpensive . It uses common brass fittings ...
 
Thanks for all the advice, I am thinking I may need to with something different. It's not a long run so maybe black pipe will be my choice instead. Better to be safe and avoid injury.
 
I use copper refrigerant line. Cheaper than water line and good for the pressure. And the sweat fittings are cheap but you have to get them at a HVAC supply place. My system is twenty years old with 175 psi compressor.
 
Either copper or steel pipe have proven to be safe for compressed air when installed properly. Long horizontal lines should be installed with a slope, and a manual drain valve installed at the low point(s) of the system. Any plastic material is subject to degradation from heat, chemicals, or UV, and plastic can act like shrapnel if it ruptures. Compressors can pump oil into the discharge as they become worn or have a mechanical failure. Copper or steel will stand up against the combination of factors better than any kind of plastic.
 
ive used 3/4" pex lines for 130psi for about 3 years now and have not had an issue. I actually have had more issues with the shut off than anything. Its rated for 200 psi, i guess i fail to see the issue...cut a chunk, copper compression fitting and move on with life...
 
and since i cant edit....

130 should have been 160, miskeyed

i dont know why condensation is brought up there should be traps or some sort of coalescer off the tank anyway.

and anybody who says a 150 psi is to much and should only need 100 psi must be working on a lawn mower...

if you think plastic acts like shrapnel what do you think black pipe acts like when it blows?

psi is psi whether its gas, oil, air, or injectors. while i wouldnt put pex on a 1440 psi gas pipeline, and your not running 25kw florescents per bulb and putting pex 2" from it, i wouldnt worry
 
The problem with PVC is it will shatter. Not just from the air pressure but a combination of the air pressure and a accidental bump into it.

Pex is better but it will not stand up long term to the petroleum your air compressor puts out. It will also shatter when compromised and do not stand up to UV.

Truck air lines; while they may look like pex they are really polyamide nylon.

High-Density Polyethylene pipe HDPE made for water and sewer is also good as it will split rather than shatter.

Black pipe is still a good choice. While polyamide nylon and HDPE would cost less on some large jobs threw labor savings on install; for a self install small job black pipe is usually cheaper than either of these.
 
At 150 psi you would be up close to the limits of PEX. What would happen is if you had a joint that didn't crimp quite right it would leak or come completely apart. Even with rubber air hose you could have that happen.

I use PVC. Every shop I've ever worked at in the last 43 years has used it. It doesn't shatter if installed and used properly. What most people do is run PVC right down to the coupler. Then when someone yanks on an air hose they break the pipe. If the PVC is adapted to steel pipe and firmly mounted to the building before the air coupling there won't be a problem. I usually weld a steel plate to an elbow so I can firmly mount it to the building.

When a PVC pipe is broken it makes a lot of noise but doesn't explode with shrapnel like people say unless someone exceeds the pressure rating of the pipe. I regulate the pressure down to about 120 psi before going to PVC.
 
Pex won't shatter like PVC as it isn't brittle. But, for a 150-175PSI system it is at is' limit.

Before anyone makes up their mind that PVC won't shatter do this Google search: pvc airline explosion

read the results, especially the ones from the OSHA and aircompressoreworks.com site.

Make up your own mind.

My shop has copper and steel.
 
It never ceases to amaze me how many folks insist on using products (such as PVC) that are not approved or marketed for compressed air when there are reasonably-priced alternatives (both metal and plastic) that ARE approved and marketed for air. Sure, PVC is cheap, easy to install and readily available. But it is not safe.
 
You can't go by anything OSHA says. Those people over exaggerate everything. They take an event where someone pressurizes the pipe beyond limits and applies it to everybody in all applications. It's just easier for them to say no air in PVC than to train their people how to tell the difference between it done right and wrong. I've seen PVC pipe broken dozens of times that were incorrectly installed yet nobody has had so much as a scratch from it. One company I worked for ran PVC down a building support beam and just put a piece of duct tape on it at the elbow end where the coupler was. This pipe was broken three or four times in the year I worked there but never did anything better to mount it.
 
>But you give no suggestions.

I didn't give any suggestions, but others did.

PEX-AL-PEX (aluminum coated inside and out with PEX) is approved for compressed air. But it's not that cheap and you won't find it at your local Home Depot. My personal choice is plain old black pipe.
 
>You can't go by anything OSHA says. Those people over exaggerate everything.

You can use that same logic to ignore any safety regulation. Hard hats, steel-toed shoes, safety glasses and ROPS are all examples of safety equipment that's unnecessary. Until, of course, that one day when you do need it.

Behind any safety regulation, there's a death or injury that prompted its adoption.
 
PEX,PVC, CPVC etc. are not approved for compressed air. They're not THAT much cheaper or easier to install than approved materials.

After all the research I did of approved compressed gas materials I chose copper. Black or galvanized pipe was cheaper but takes a lot more time to cut and thread.

I just finished construction on a 3000' shop. I ran about 40' of 3/4" L copper and another 60' of 1/2". M would work but is not quite as stiff. Point is the material cost with fittings valves, uni strut,clamps etc. was about $250.00 I already had the compressor, filters, regulators, hoses etc from the other building I moved out of. I spent half a day getting it all installed

I ran all the water lines for exterior hose bibs in pex. It sure was faster to install but not nearly as pretty as the copper.

I have seen PVC systems that didn't fail. However it doesn't handle time or the heat of the compressed air very well and drooped. Looked really bad. Securing at point of use is mandatory. Mechanics jerking on hose broke PVC off the wall.
 
I installed 1" PVC in my shop thirty years ago. Sch 40 (operating rating of 270 psi), but only operating at 120 psi. Came in the next day after a cold night and wondered what all the white stuff was on the floor. Ahhh! No pipe on the wall. It fractured and blew all over the shop. I don't know why but I never used it in air service again.
 
Copper here, I built the house so it's in the walls and out of sight and trouble. I did black iron for my gas pipes; miserable job. Only after I had half of it done, and bought another batch of pipe, did I find out the first batch was .020" oversize and the Rigid thread die was tearing the threads up and they leaked. That was 25 years ago, so I did get it to seal and stay sealed.
 
Yeah, and if you do the search I suggested and read the non-OHSA info you'll find that no maker, or any other organization, approves PVC for compressed gas use. And LOTS of pics of broken pipes. Sunlight or fluorescent lights will degrade it and it becomes very brittle. I hit a piece in my yard with a little electric weedeater, really small line, and it shattered like glass. Had it be full of compressed air, there would have been a lot of shrapnel flying.
 

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