Author Topic: PEX for plumbing airlines?  (Read 793 times)

Offline Uncle Buck

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PEX for plumbing airlines?
« on: April 11, 2018, 02:29:33 PM »
From what I have been able to determine, PEX is not rated or intended by the manufacturer to be used for compressed air systems. Various opinions and information I have found indicate that unlike black gas pipe PEX will not dissipate the heat of compressed air. Additionally some opinionated that PEX would deteriorate under the UV light of shop lights and that fine amounts of compressor oil would contribute to PEX failure. Beyond that most reported that upon failure of PEX unlike PVC rupturing and shooting shards of PVE everywhere, PEX line will split, much like a copper line would if it failed.

After reading a number of opinions and pages of experiences on other web sites my takeaway is that while PEX is not rated for compressed air systems if it does fail human welfare will not be in jeopardy. As for the comments regarding moisture content in the air I think that dryers, filters and drains could successfully control that.

I am looking at plumbing my shop in the next few months and I am tempted to do it with PEX. I can get all of the 3/4" PEX line I want to do the job for nothing. The clearest gain being ease of installation, the second being a great cost savings for material. I am posting this looking for the opinions of the membership here that have knowledge of PEX and using it for a compressed air system.
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Offline DeadNutz

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Re: PEX for plumbing airlines?
« Reply #1 on: April 11, 2018, 02:53:12 PM »
I have never thought about using PEX for air. I did use it in the barn for the horse waterers and it is buried and not exposed to UV. As far as the failure mode goes, I guess it is not a danger unless you happen to be standing right next to where it splits. I know the fittings are not cheap and the tools made to work with the fittings are pretty pricey. Do you have access to the tools? I thought about plumbing the shop for air but the footage required would be high with the 16' ceiling. I have enough hose to reach anywhere I need to reach and I have been coiling air hose all my life so no big deal.

Offline Uncle Buck

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Re: PEX for plumbing airlines?
« Reply #2 on: April 11, 2018, 02:59:14 PM »
I have never thought about using PEX for air. I did use it in the barn for the horse waterers and it is buried and not exposed to UV. As far as the failure mode goes, I guess it is not a danger unless you happen to be standing right next to where it splits. I know the fittings are not cheap and the tools made to work with the fittings are pretty pricey. Do you have access to the tools? I thought about plumbing the shop for air but the footage required would be high with the 16' ceiling. I have enough hose to reach anywhere I need to reach and I have been coiling air hose all my life so no big deal.

Have access to tools, and possibly a number of the fittings needed as well so those costs are not factors either. The only real issue buggering me is failure and possible injuries. But to me a split type failure should not equate to injuries like a shattering under pressure type failure. Failure of the line would be of little consequence either as I will be doing most of the system at negligible cost.
You boys better hold on cause i'm gonna have to stand on it!

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Andrew Jackson quote: But you must remember, my fellow-citizens, that eternal vigilance by the people is the price of liberty, and that you must pay the price if you wish to secure the blessing.

Offline DeadNutz

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Re: PEX for plumbing airlines?
« Reply #3 on: April 11, 2018, 03:06:29 PM »
Can you use other fittings and clamps with that stuff? As far as failures, if losing a length due to a split that is up to you. Costs for new underwear might go up if it split where you are standing. lolx

Offline Uncle Buck

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Re: PEX for plumbing airlines?
« Reply #4 on: April 11, 2018, 03:37:02 PM »
There is a huge part of my brain married to the idea that I want/need black gas pipe to do this job. Copper would be even more of a nightmare to install than black iron pipe due to the inaccessible locations where lines would need to be sweated for installation. Too many fire risks to even consider copper. That and there is literally no room for installing whatever choice of airline in difficult to accessed areas. To install I will have to make long runs at the top plate at ceiling joist height. To even get there things will have to be unloaded to allow access for installation. Beyond that I can see lines being attached to the underside of the ceiling joists to hang hose reels.

In one sense, failure around the perimeter would be at what, maybe 10' height and most all of that line would be blocked by the storage of all manner of boxes, car parts etc. I have also considered doing the tough to access areas in PEX but use black pipe for the drops, and the first 8' coming from the compressor. 
You boys better hold on cause i'm gonna have to stand on it!

NEED A 1/2" BONNEY STREAMLINE COMBINATION AND ANY OVER 13/16" TOO!



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Offline Matt_T

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Re: PEX for plumbing airlines?
« Reply #5 on: April 11, 2018, 03:48:39 PM »
PEX is polyethylene and you can buy polyethylene tubing for compressed air use. Also IIRC the "rapidair" systems are PEX-AL-PEX. Doubt a little oil carryover from the compressor is gonna cause any chemical compatability issues.

Working pressure might be a problem if you're running 175-200 psi so you can run impacts on 50' of 1/4" hose. Compressed air temperature shouldn't be an issue because the tank knocks a lot of the heat out before it ever hits the distribution piping. Biggest temp derate consideration is gonna be ambient up in the roof.

My current plan is to run PEX overhead with galv pipe drops. Running PEX drops will be expensive and difficult to mount securely.

Offline Uncle Buck

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Re: PEX for plumbing airlines?
« Reply #6 on: April 11, 2018, 04:13:48 PM »
I think you should rethink running galvanized drops. If you can copper would be great, with black pipe closely following. Of course black pipe will tend to produce rusty water. Supposedly galvanized is supposed to flake off over time filling filters, and or damaging air tools. I am not sure that galvanized pipe is even galvanized internally, I am just sharing what I have read about using galvanized for compressed air systems.

As for line pressure, I don't think my compressor is even good for more than 125 at the tank and the line I have access to is rated for something like 160 PSI or more.
You boys better hold on cause i'm gonna have to stand on it!

NEED A 1/2" BONNEY STREAMLINE COMBINATION AND ANY OVER 13/16" TOO!



Andrew Jackson quote: But you must remember, my fellow-citizens, that eternal vigilance by the people is the price of liberty, and that you must pay the price if you wish to secure the blessing.

Offline slip knot

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Re: PEX for plumbing airlines?
« Reply #7 on: April 11, 2018, 04:56:00 PM »
UV shouldn’t be a big issue. I ran a temp led line to an op shelter 10yrs ago. We never covered it up due to the temp nature and all.  Well it’s held up great in the hot S Tx sun. Your shop exposure should be fine.
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Offline Uncle Buck

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Re: PEX for plumbing airlines?
« Reply #8 on: April 11, 2018, 06:09:13 PM »
UV shouldn’t be a big issue. I ran a temp led line to an op shelter 10yrs ago. We never covered it up due to the temp nature and all.  Well it’s held up great in the hot S Tx sun. Your shop exposure should be fine.

I figured if I had areas the pipe runs close to lights I could always cover the exposed areas in pipe insulation.  shrugx
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Offline Matt_T

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Re: PEX for plumbing airlines?
« Reply #9 on: April 11, 2018, 10:42:22 PM »
I think you should rethink running galvanized drops. If you can copper would be great, with black pipe closely following. Of course black pipe will tend to produce rusty water. Supposedly galvanized is supposed to flake off over time filling filters, and or damaging air tools. I am not sure that galvanized pipe is even galvanized internally, I am just sharing what I have read about using galvanized for compressed air systems.

In the past 30 years I've seen lots of problems caused by rust and none caused by zinc flakes.

As for line pressure, I don't think my compressor is even good for more than 125 at the tank and the line I have access to is rated for something like 160 PSI or more.

IIRC that 160 is at room temp and reduces with .temperature. Doubt it'll be a problem with 125 psi but check the hot specs for your pipe against expected attic temperature.

Offline pepi

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Re: PEX for plumbing airlines?
« Reply #10 on: April 11, 2018, 10:53:16 PM »
I ran galvanize pipe, now installed 25 + years. I've read the same about the partials, but never seen any proof. Have come to the conclusion, it is more of theory that could happen. Like getting hit with a lighting bolt could happen.

I have a galvanized motorcycle trailer, bought it 1973, been sitting in the weather, Miami and GA, never covered to this day. The only place the coating has failed was where some rubbing on the top of the fender, caused by a load shifting.


If asked I'd say galvanized pipe for air lines is fine. Compressor is out side, my system is simple. One main line, one drop with T and drain. Regulator plumbed from the T, from the regulator to a hose reel and 100ft rubber hose.

I have two drops for water drains, one out side in the compressor feed and the one inside before the regulator, that also has a moisture drain.  Hose reel is next to the garage door, very handy can run it outside and all over the inside of the shop area.

Pipe run out side at floor level of garage, 90 thru wall, up the wall and across the header. The down next to the garage door frame, seen in the picture,1/2 down and over to the regulator and hose reel.

Simple and useful 50ft of pipe or so.

Greg
« Last Edit: April 11, 2018, 10:59:35 PM by pepi »
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Offline slip knot

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Re: PEX for plumbing airlines?
« Reply #11 on: April 11, 2018, 10:55:39 PM »
I'm not too sure what the exact burst pressure is for pex but it should be easy enough to test. get a piece, cap it off and pressure it up.

The one thing that really sold me on pex water lines is the fact it doesn't burst when it freezes. just swells a bit then goes back down when thawed.

As for rusty black iron, I ran 3/4in black iron in my shop back in 04. haven't had any issues with rusty water. I keep the tank drained tho. And I keep the compressor on all the time.
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Offline Conductor562

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Re: PEX for plumbing airlines?
« Reply #12 on: April 11, 2018, 11:19:20 PM »
When I do mine it will be PEX. There’s couple companies that offer PEX kits just for air lines, but they’re expensive for what they are and could be user assembled for far less.
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Offline skfarmer

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Re: PEX for plumbing airlines?
« Reply #13 on: April 12, 2018, 01:23:43 PM »
i have galvanised pipe and it has been in place for 5 years or so now. i have not seen or noticed any issues with flake.

i think pex may be a good solution for you if you keep it out of the attic. as was said, the high heat may be an issue there.
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Offline DeadNutz

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Re: PEX for plumbing airlines?
« Reply #14 on: April 12, 2018, 01:40:33 PM »
There are the 3 colors of PEX and I don't know if there are differences in the different colors such as the red for hot water or if it is simply color coding. Some of the problems with PEX seems to be in the older and cheaper fittings. Here is an interesting read: https://www.pexuniverse.com/problems-pex-pipe-and-how-prevent-and-fix-them

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Re: PEX for plumbing airlines?
« Reply #14 on: April 12, 2018, 01:40:33 PM »