Pex for air lines

[RandyLittrell 3,877]

As some of you know, I just redid all my plumbing and gonna have some pex left over. I have the tools and plenty of fitting left as well and figured I might as well see if its okay to use.

 

I thought I had read a long time ago it was not okay, but I see lots of folks using it and testing it too. Can't think of an easier way to run air lines. 

 

Seems like it's just fine to me, but I know you guys always have the right answers.

 

What do you guys think? 

 

 

 

Randy

[Jeff-C175 7,199]

The "RapidAir" kits sure look like PEX to me:

 

https://www.northerntool.com/shop/tools/product_200484023_200484023

 

Looking further though, this is described as HDPE/Aluminum

 

https://www.northerntool.com/shop/tools/product_200484021_200484021

 

Is HDPE any different than PEX?  HDPE is High Density PolyEthylene, PEX is Cross Linked Polyetheytlene.

 

PEX used for hot water heating has the aluminum core also.

 

What's the pressure rating on your PEX?  I think that would be the determining factor, no?

Edited February 25, 2021 by Jeff-C175

[8ntruck 6,991]

What does your local building code say about materials for air lines?

[DennisThornton 4,769]

4 hours ago, Jeff-C175 said:

The "RapidAir" kits sure look like PEX to me:

 

https://www.northerntool.com/shop/tools/product_200484023_200484023

 

Looking further though, this is described as HDPE/Aluminum

 

https://www.northerntool.com/shop/tools/product_200484021_200484021

 

Is HDPE any different than PEX?  HDPE is High Density PolyEthylene, PEX is Cross Linked Polyetheytlene.

 

PEX used for hot water heating has the aluminum core also.

 

What's the pressure rating on your PEX?  I think that would be the determining factor, no?

My last employment's shop needed to run more air lines and I did some research and decided not to run PEX.  We stocked it too.  Seems we thought it would work but read not to use it...  Just can't remember why... 

The aluminum lining is an oxygen barrier for some heating systems.  Not sure why it would be offered for shop air supply. 

Definitely did not choose PVC!  Shatters with shrapnel!  Ended up just running a length of rubber air hose.  I ran galvanized in my shop decades ago.  Expensive but no issues. 

 

I'm curious what this thread turns up!  I'm setting up two more shops that need air.

 

Edit:  Just read this.  Probably why we didn't use PEX:

Warning! Do not use PVC pipe, or PEX and similar plumbing fittings for compressed air. They’re not rated for high pressure and can fracture or explode under pressure.

Edited February 25, 2021 by DennisThornton

[953 nut 55,098]

When I built our house I did all of the supply lines in PEX. Our plumbing code calls for a 100 PSI test pressure and without water in the lines there were fittings that had some minimal leakage. I filled the system with water and put 100 PSI air on top of that and there were no leaks.

The air lines in my shop are one inch Sch. 40 PVC which is suspended from the ceiling out of harm's way. The compressor is in the barn fifty feet away and there is a condensation drain on the lowest point of the underground pipe run.

[JoeM 7,871]

Maybe static electricity is an issue? I know at work we ran plastic air line and it had to have a copper drain ad a ground. The air rated stuff is a little more money. Not worth the risk??

[DennisThornton 4,769]

Might take some serious pressure but PVC can shatter with shrapnel.  I know it's in shops for air but Google "PVC air line explosion" for lots more. 

[Jeff-C175 7,199]

1 hour ago, 953 nut said:

out of harm's way

 

But will YOU be out of harms way when the PVC explodes and shoots sharp shattered shards (how's that for alliteration?) of PVC in every direction?

 

Every single thread I've seen on the internet regarding PEX for air lines devolves into a discussion of PVC ... but it's necessary because it is a GENUINE safety hazard!

 

Use PVC and roll the safety dice.  It's YOUR safety!

 

 

Here's what I have observed with PVC over the years.  BRAND NEW PVC pipe is somewhat 'supple'.  AGED PVC pipe becomes progressively more brittle with age.  

 

My  potable well water supply is piped in PVC from the point of entry to the home in the utility room to where it transitions to copper, maybe about 10' of PVC altogther.  The system was installed about 10 years ago.  The first 5 years, no problems.  THREE TIMES in the past 5 years I have had cracked pipes and fittings that needed repair due to the pipe becoming brittle with age.  My system runs at 55 PSI max.  I'm at the point of getting ready to re-plumb with copper due to the issues.  I need to install a 'water cop' to shut the pump down in the event of catastrophic failure.

 

Roll the dice, try to beat the odds.

 

Edited February 25, 2021 by Jeff-C175

[Jeff-C175 7,199]

21 minutes ago, JoeM said:

Maybe static electricity is an issue?

 

That may be the reason for the HDPE-ALUMINUM for sure!  I can see static electricity being an issue.

[peter lena 8,583]

randy, have seen pex  tubing  used for air lines, without issue, the best option that you have is to use a , BALL VALVE BEFORE YOUR PEX ,START FITTING , that way if there was ever an issue , it would be a quick and easy shut off to contain your start , pete

[DennisThornton 4,769]

23 minutes ago, Jeff-C175 said:

 

That may be the reason for the HDPE-ALUMINUM for sure!  I can see static electricity being an issue.

Static sparks are an issue with vacuum lines and dust but I can't imagine a purpose in air lines...  Blocks O2 so I suppose all of air too but so?  Other than preventing rust in heating systems.

[Jeff-C175 7,199]

6 minutes ago, DennisThornton said:

preventing rust in heating systems

 

That's the biggie for hydronic systems.  O2 is a killer for cast iron boilers.

 

Having worked with PEX-AL-PEX I do know that it is MUCH more rigid than standard PEX so perhaps that's the reason RapidAir chose that?  Less supports needed, holds shape better?  I dunno.

 

Maybe a contact to RapidAir would yield some answers?

Edited February 25, 2021 by Jeff-C175

[DennisThornton 4,769]

24 minutes ago, peter lena said:

randy, have seen pex  tubing  used for air lines, without issue, the best option that you have is to use a , BALL VALVE BEFORE YOUR PEX ,START FITTING , that way if there was ever an issue , it would be a quick and easy shut off to contain your start , pete

We were going to install PEX but read a couple warnings not to.  Commercial environment so we didn't want to risk it.  I've broken PVC and it does shatter but I can't break PEX!  No idea other than what I've read why PEX can't be used and unless I find some reason soon I'm most likely going to use it.  Too cheap and easy not to unless there's something missing.  It sure isn't going to blow with shards and shrapnel.  

 

By the way, PVC has long been used for high efficiency boilers but that is changing.  Pretty sure no longer permitted in Canada and probably being phased out here in the states even though it was/is specified by some manufactures.  Biggest concern that I've seen and read is near the boiler where it is hotter and has more chemicals, turns yellow and degrades.  Was never rated for venting use by the PVC manufacture, only the heater manufacture suggested it.  There is a company now making PVC rated for heater venting.  Hot air comes out of a high volume air compressor and cools either in a cooler or as it goes down the lines.  I could see PVC degrading right at the compressor.

[DennisThornton 4,769]

5 minutes ago, Jeff-C175 said:

 

That's the biggie for hydronic systems.  O2 is a killer for cast iron boilers.

 

Having worked with PEX-AL-PEX I do know that it is MUCH more rigid than standard PEX so perhaps that's the reason RapidAir chose that?  Less supports needed, holds shape better?  I dunno.

 

Maybe a contact to RapidAir would yield some answers?

Yeah, I'd prefer the PEX-AL-PEX over just PEX air but still wonder if it's needed.  I just can't imaging PEX causing damage upon failure.  Not like PVC!

[squonk 41,038]

Do not run plastic for air. You need metal to help cool the compressed air so the moisture condenses in it so it can be trapped by a water separator. Also Do not  install the separator right on the compressor. 

 

https://cached.tptools.com/Images/airline-piping-diagram.pdf

 

Edited February 25, 2021 by squonk

[Jeff-C175 7,199]

20 minutes ago, DennisThornton said:

I just can't imaging PEX causing damage upon failure.

 

Me either.  I can see it 'rupturing' perhaps, but certainly not sending sharp projectiles into your eyes or other organs.

 

[posted just before seeing Squonk's reply!]

 

On the 'garage journal' board there was some discussion regarding moisture retention.  Their assertion was that plastic lines don't cool the air as copper or steel would and thus any entrained moisture remains in the air rather than condensing to be trapped and removed.

 

I guess that makes some sense... but on the other hand, if PEX works so well in hydronic systems at moving the heat through itself, why would in not also cool air in order to facilitate moisture removal?  

 

If one had a need for DRY air, they should invest in a proper DRYER system!

 

Edited February 25, 2021 by Jeff-C175

[squonk 41,038]

It's explained in the PDF I copied on my post,

[DennisThornton 4,769]

1 minute ago, Jeff-C175 said:

 

Me either.  I can see it 'rupturing' perhaps, but certainly not sending sharp projectiles into your eyes or other organs.

 

On the 'garage journal' board there was some discussion regarding moisture retention.  Their assertion was that plastic lines don't cool the air as copper or steel would and thus any entrained moisture remains in the air rather than condensing to be trapped and removed.

 

I guess that makes some sense... but on the other hand, if PEX works so well in hydronic systems at moving the heat through itself, why would in not also cool air in order to facilitate moisture removal?  

 

If one had a need for DRY air, they should invest in a proper DRYER system!

 

I think PEX works for hydronics but not all that well, hence the great footage required and radiant takes its time.  I always intended to put a precooler on my compressor when I had the shop but never did.  Read different ways to make my own and one could today even with PEX.  I still think galvanized is the best but...  And with the cost of copper!

[JoeM 7,871]

Rapid Air isn't Nylon? guess not but not sure what the liner may be made of. 

 

More oil resistant 

Edited February 25, 2021 by JoeM

[squonk 41,038]

The metal pipes will stay cooler than plastic in a warm summer shop. If you're just pumping up a tire once in a while of blowing the dirt off your workbench so you can find it, run what you want. But any serious sandblasting sanding ect., run galvanized. I have 3/4" with risers and multiple drains in my shop.

 

[DennisThornton 4,769]

I ran high volume tools including a decent sized pressurized sand blaster.  Sand blasters don't like moisture!  But not all home or hobby shops are going to use that kind of volume.  Filling a tire or blowing off dust is different.  If you are going to use large CFMs you need to deal with moisture somehow.  I used galvanized and every drop down had a separator and drain but once the galvanized warms up it no longer condenses.  And indeed, plastic won't cool like metal.

[Jeff-C175 7,199]

15 minutes ago, squonk said:

run galvanized.

 

That PDF says no.

 

Quote

Use Black Iron Pipe only. We do not recommend galvanized metal pipe, as galvanization can come off the inside of the pipe, clogging separators and regulators. Do not use PVC pipe, as PVC will not help cool the air; and glued joints often separate. Avoid copper tubing, as it is easily damaged; and soldered joints can come loose under pressure (Safety Hazard).

 

This is also one of the reasons I've heard to not use Galvanized for natural gas piping.  That and supposedly some components of natural gas 'attack' the zinc and cause it to 'powder'.  

 

On the other hand, I would expect that some rust would occur in black piping and cause some of the same issues.  I've seen air filters on CA systems clogged with rust particles.

Edited February 25, 2021 by Jeff-C175

[Jeff-C175 7,199]

14 minutes ago, JoeM said:

Rapid Air isn't Nylon?

 

No, High Density Polyethylene with Aluminum inside.

[squonk 41,038]

I rather have galvanize break off instead of rust. I've had my set up over 30 years with no issues.

 

I ran about 100ft of black iron at my B-i-L's shop about 20 years ago. No issues but he never drains his compressor (Can't get to the drain with all the junk piled around it!) 

Edited February 25, 2021 by squonk

[JoeM 7,871]

I seen this it looks like it has a poly liner too. And there are other that are just poly

 

Maxline Rapidair M3800, 1/2" Master Kit 100 ft. 3 Outlets

Set up a compressed air system with the 1/2 in. Maxline Master Kit with 3 air outlet locations. The Maxline tubing has an aluminum core sandwiched between an inner and outer layer of polyethylene. Tubing can be mounted on wall surfaces, in wall, or buried underground or concrete. Tubing holds any hand bent shape. Reduce shop clutter with this industrial compressed air piping system. No glue, soldering or crimping needed. Simply cut the tubing to length, insert in the fitting and tighten. Easy to expand with more air outlet locations or modify later.