I would think the effects of water hammer would be more stressful on PEX than running air through it could ever be. My guess is they don't want a potential lawsuit since they haven't tested it for uses other than water supply.
I would think the effects of water hammer would be more stressful on PEX than running air through it could ever be. My guess is they don't want a potential lawsuit since they haven't tested it for uses other than water supply.
When I began my apprenticeship in the pipe trades all the soil pipe was lead and oakum. You could fabricate an entire bathroom on the floor, put it on a Hy-lyft and raise it into a couple hangers and you were done. Then we went to no-hub. As the apprentice I quit working with pipe and got to drill 3/4" Redheads into concrete decks all day for all the hanger that were necessary to keep the pipe where it was supposed to go. Same when we went from welded to Victaulic. If you use the pex, put a lot of hangers on it but let it move and put a hanger on each side of every fitting. If one of the fittings blows you will end up with a metal ended whip flipping around to the distance of the last support. There are plenty of things that can hurt you in a shop. Much of our efforts are in reducing them. I don't want to be doing some close work on a bandsaw when an air line lets go.
I ran across a website that makes air fittings for pex. http://www.logic-industries.com/airbase.htm I am wondering if they have independently determined that pex is ok for air?
Last edited by Ole Anderson; 11-28-2018 at 7:08 PM.
NOW you tell me...
Lee Schierer
USNA '71
Go Navy!
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Pex is not brittle like PVC. Pex is cross linked polyethylene that is why it is flexible. It should rupture rather than shatter if it fails. Polyethylene is what the gas companies use now for most low and medium pressure underground pipelines and is used for most directionally bored pressure water and sewer lines. Not saying you should use it for air lines, but I would, although I like using copper. Frankly I am using an old rubber 3/8" air hose as a distribution line, probably going on 25 years now, picture doesn't show it well, but it is behind the orange hose hanging on the hook. Notice shock mounts on bottom of legs and tank drain?
Last edited by Ole Anderson; 11-28-2018 at 10:54 PM.
NOW you tell me...
I would like to see answers on this...
So, I think everyone agrees that the manufacturers of PEX tell you it's not rated for air. Wouldn't the PEX manufacturers love to open a new market for their product if it was safe? Because some people have used it and not had an issue does not make it safe or OK. It means they didn't have a problem with it.
If you think anything is safe, or okay, I want what you're having. Anything and everything can and will fail. Usually at the least opportune moment.
Who knows why they don't? My guess is they can barely keep up with demand as is as they keep pounding up plants and warehouses, and getting some osha/CEL rating for compressed air probably costs a bloody fortune. Second guess is it is worthless at low temperatures. -40º does weird things to plastics and it might become a claymore at 100 psi at those temps. Who knows. It worked just fine for me, and it worked just fine for the cabinet shop up the street from me. And, I was running 180psi in the old shop. Way more than you need.
If you don't want to use it fine. It's cheap, it's ugly, it's easy to modify, and it holds heat way too well. When I plumbed my new shop for air, I did it all in aluminum pipe. I don't know why you'd bother with anything else after putting that system together.
There is only one answer;
Stay within the manufacturers design basis criteria, or accept the risk of operating outside of it.
As I stated earlier, I have installed reels, upon reels, of flexible tubing for a living.
Would I use PEX for air at home? Yes, I wouldn't hesitate.
Would I let someone pay me to install PEX for air? No!
"The first thing you need to know, will likely be the last thing you learn." (Unknown)
Note that PVC pipe inside a shop takes about 20-30 years to breakdown and fail catastrophically. Pex is not supposed to be left outside in the sun for more then 30 minutes or so. If pex is going to fail in compressed air duty how long will it take for the stresses to let go? Anyone have a shop plumbed in pex 30 years ago? is it protected form sunlight by the windows? What is the plastic pipe that got banned about 10 years after it was first allowed for water.
Bil lD
Where in the word does that come from? 30 minutes? We have plumbed numerous ground up homes with pex that probably saw more than 30 minutes of sun between manufacture and delivery to the job. Are the reels rushed from manufacturing to the delivery trucks with strict log sheets as to how often the door was opened on the tractor and trailer? Then unloaded at the distributor in the dark of night? Delivered to our plumbing supply house and then to us strictly under the darkness of night? What about a facility floor or a pole barn for that matter that has radiant in the floor? Do they cover the tubing with napkins while they attach it to the mesh so its ready for the concrete truck to come in a couple days and deliver the concrete? The reels are shipped in clear shrink wrap for gods sake? They are not even in a box?
Excuse my sarcasm but we have installed MILES of pex in homes, concrete, and so on,..... 30 minutes? Thats just plumb nuts.
I would NEVER install PVC air lines in my shop, and we have installed miles of PVC. And I probably wouldnt install pex either because we run 175PSI mains and it gets warm in here so the 160 PSi at 7X degrees F would shy me away even though Im sure it would hold and I wouldnt be worried about at deadly failure.
These things are hilarious to read. Why in the world would I ever plumb my, or someone elses, home with a material that was so fragile that a mere 30 minutes of sun exposure is an issue? That makes ZERO sense. There are more than 30 minutes of reflected sun exposure in a basement with 2 small windows in it to fry the pex? The pex in a new home is often going in while the home is wide open, no windows, being roughed in... the reflected sun is hours, weeks, months.
Now people will talk about he UV from fluorescent lights and the pex... good god.
More info
Here is a link the engineering specs for PEX. UV exposure is 1.5.2. 60 days is defined as a short time period that PEX can be exposed to.
https://api.ferguson.com/dar-step-se...UCT_ID=2886838
"The first thing you need to know, will likely be the last thing you learn." (Unknown)