Pex for air lines

[Jeff-C175 7,199]

14 minutes ago, squonk said:

Can't get to the drain with all the junk piled around it!

 

Maybe the junk will cushion the blow when the rusted out tank ruptures!  

[Jeff-C175 7,199]

Just talked to a support tech at RapidAir.  

 

HDPE-AL-HDPE is NOT the same material as PEX-AL-PEX.

 

He claims it's more durable / stronger with a continuous working pressure of 200 PSI and a burst pressure of 600 PSI.

 

He's sending me some tech specs on the tubing via email.

 

Don't know about temperature derating yet.

 

[pacer 3,168]

Heh! this is one of those topics like "which is the best oil? etc" there will be MANY different experiences/opinions..... 

 

Well heres mine concerning an air compressor, 80gal tank with reg set at 90psi on/ 140psi off producing 18-20 cfm. 45 yrs ago when I built my 16x32 shop I ran black pipe down side and rear walls with some 6 outlets. After about 5-6 yrs I added a 12x32 addition to the shop and obviously wanted air in the new area. On starting to connect to the old black pipe I found it was a rusted mess! Ripped it all out and having a buddy that had plumbed his shop with schedule 80 PVC, I started replumbing with that - adding some 150' of it with an outlet bout every 6' and 4' high This was some 35yrs ago.

 

Well of course as time went by I would need another outlet here/there etc.and adding one is so easy with the PVC Only problem I had/have is threading a brass/steel air coupler or hose into the PVC, very touchy about splitting or leaking. IIRC, I've had 2 ... maybe 3 elbows split just enough to hear the 'hiss' (in fact I have a 'hisser' right now that I need to correct.) I run a blast cabinet and an outdoor blast rig along with about 8-10 air tools all using at the noted 130-140psi.

 

So, along with my many yrs of usage and actually NO real problems, I have two friends that also have their shops ran with schedule 40 some 20-25yrs ago and no probs there either.

 

Of course, living here in the south with our much warmer climate could very well be a factor in using PVC.......

 

 

 

 

 

[RandyLittrell 3,877]

2 hours ago, squonk said:

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

 

 

 

I have been researching diy air driers and am going to run a length of copper across the wall a bit and back with a drain before it goes into the compressor tank to reduce water into the tank as well as the system

 

I didn't know a pex question was gonna turn out to be like a best oil question!

 

 

 

 

Randy 

 

Edited February 25, 2021 by RandyLittrell

[DennisThornton 4,769]

3 hours ago, Jeff-C175 said:

 

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.

 

I'm surprised!  My house was built in the early 80s, has had 60-80 psi for 20 years and never an issue.  I managed a hardware store for a few years and helped many a plumber and can't remember a problem with PVC.  Don't want to use cold water only white PVC where CPVC should be used.  We stocked some copper but seldom sold any.

[DennisThornton 4,769]

1 hour ago, pacer said:

Heh! this is one of those topics like "which is the best oil? etc" there will be MANY different experiences/opinions..... 

 

Well heres mine concerning an air compressor, 80gal tank with reg set at 90psi on/ 140psi off producing 18-20 cfm. 45 yrs ago when I built my 16x32 shop I ran black pipe down side and rear walls with some 6 outlets. After about 5-6 yrs I added a 12x32 addition to the shop and obviously wanted air in the new area. On starting to connect to the old black pipe I found it was a rusted mess! Ripped it all out and having a buddy that had plumbed his shop with schedule 80 PVC, I started replumbing with that - adding some 150' of it with an outlet bout every 6' and 4' high This was some 35yrs ago.

 

Well of course as time went by I would need another outlet here/there etc.and adding one is so easy with the PVC Only problem I had/have is threading a brass/steel air coupler or hose into the PVC, very touchy about splitting or leaking. IIRC, I've had 2 ... maybe 3 elbows split just enough to hear the 'hiss' (in fact I have a 'hisser' right now that I need to correct.) I run a blast cabinet and an outdoor blast rig along with about 8-10 air tools all using at the noted 130-140psi.

 

So, along with my many yrs of usage and actually NO real problems, I have two friends that also have their shops ran with schedule 40 some 20-25yrs ago and no probs there either.

 

Of course, living here in the south with our much warmer climate could very well be a factor in using PVC.......

 

 

 

 

 

I know there's lots of PVC air supply systems out there and I'm wondering if the horrendous pictures are from a switch failure and over 200 psi blowing it apart.  Don't know, just that I'm not using it.  Might use PEX though!  Got to read some more.  No hurry yet.

[Jeff-C175 7,199]

56 minutes ago, DennisThornton said:

I'm surprised!

 

I am too actually.  Being that this was installed by a reputable well drilling installer one would think that if there were that many problems with PVC it would behoove them to use something different.  

[Zeek 2,286]

Just my based on personal experience . . .

I went through the PVC debate too. It didn't make sense to me, so I went with it. I used PVC in my old shop for years. It is rated for 300+ PSI or more depending on diameter. I used copper for the drops at the ends and a flex line a the compressor. The compressor was 125 PSI max. Zero issues. Mine was not subject to freezing temperatures - 40° at lowest, but I'm not sure that even matters. Why would you be concerned about it blowing apart with air, but not blowing apart with water in it If it takes 300 PSI water pressure, it takes 300 PSI air pressure. You can use PEX the same way if the compressor pressure does not exceed the PEX PSI rating. Contractors air pressure check home plumbing PVC for leaks after install on new construction. That doesn't blow apart. There are an infinite number of vehicles on the road with plastic air lines, although that it not PEX. Don't hate me, just saying it worked for me for 10+ years.

Edited February 25, 2021 by Zeek

[Jeff-C175 7,199]

38 minutes ago, Zeek said:

Why would you be concerned about it blowing apart with air, but not blowing apart with water in it

 

The difference is in the amount of STORED ENERGY.

 

Since water can't be compressed there is very little (to no) stored energy.

 

Air being compressed stores an incredible amount of energy and will erupt with explosive force when something gives way.

 

Pressurize a tank of water to 100 PSI and put a round from a 30-06 through it.  Almost nothing happens..

 

The same size tank with 100 PSI of AIR will EXPLODE and go explosively at a high speed in whatever direction it chooses, possibly shooting schrapnel along with it.  God help you if it heads in your direction.

 

A pressurized water tank is a DUD.

A pressurized air tank is a BOMB!

 

Another way to think of it is this:

 

A 100 gallon tank of water holds 100 gallons if it's at ambient pressure, or at 100 PSI (example).  When and if the tank springs a leak, the water takes the same volume of space as it did when compressed.  There is NO expansion.

 

A 100 gallon tank of air at 100 PSI holds about SEVEN TIMES the volume of air at ambient pressure.  That is the stored energy that causes explosive force when the Kraaken is released.  The stored air instantly expands to it's original volume ambient pressure with much fanfare and force.

 

Edited February 25, 2021 by Jeff-C175

[DennisThornton 4,769]

I just read some plumbing code that 5 psi is used to test PVC plumbing.  Other plumbers said that water should be used to fill and then the air.

I've already said that there are many PVC air supply systems out there but we didn't do it in the repair shop at the hardware store because of OSHA and it being a commercial exposure.  I'm not going to do it at home because when PVC fails it could be very ugly and I'm not taking that chance, (though I take others...)  I might very well go with PEX though, unless someone here or elsewhere scares me off that as well.  Actually I may have enough galvanized to run what little I need...  But PEX is SO much easier to run!  And to change!  And to add on!

 

Any examples of PEX air line failures?  Lots of pics of PVC failure online!  Enough that I'd think it would cause a pause!

[wh500special 2,163]

We all get away with things that are probably not ideal all the time.  We speed.  We jaywalk.  We tear the tags off our mattresses. 

 

Some of us even use PVC for compressed air.

 

PVC isn’t a particularly strong material and it can embrittle with age, especially when exposed to UV light (sun or fluorescent lighting), heat, temperature cycling, and other things.  It’s not very impact resistant and long exposure to vibration can be tough on it. 

 

But it is great for water piping.  It’s corrosion resistant, easy to join, and likes the relatively low pressures and constant temperatures it sees. There is little dissolved O2 in a water pipe, so the inside surface of the pipe isn’t as subject to oxidation as in an air-filled pipe.

 

In a compressed air system, PVC really is a ticking time bomb.  It can last for 30 years, or can blow after a week.  Won’t really know until it happens.  Since it hardens somewhat with age due to the effects of the plasticizers leaving and general oxidation taking a toll, when it does let go it will usually do so explosively.

 

Remember seeing a lot of convertible cars through the years with yellowed and cracked flexible plastic windows?  Those are PVC.  Unlike with all of the guys on this forum, age doesn’t make it better.

Compressed gases at any pressure are far, far, far more dangerous than a pressurized liquid at the same pressure.  The forces they exert in the walls of the pipe are the same at any given pressure, but compressed air is like a big spring waiting to release its energy all at once.  Liquids don’t compress, so they do not store energy like a gas does.  It’s why popping an air-inflated balloon is so much more exciting than popping one completely filled with water.

 

 

(aside: steam explosions are so fierce because they are essentially compressed gas explosions.)

 

PVC can work for a long time.   But it might not.  It’s a gamble.

 

(warning:  speculation alert) Why not PEX for compressed air?  My guess is just that it’s not rated for pressures high enough to give sufficient headroom (safety factor) above the normal operating pressures of a compressed air system.  It is probably fine, but since consumers and installers can’t be trusted to do the right thing it’s not going to be recommended by the PEX makers or sellers.  If it was carrying a pressurized fluid and it ruptures, it’s just a mess.  Rupturing with pressurized gas is a different story.

 

Steve

[Jeff-C175 7,199]

They aren't doing AIR but WATER, this is interesting and illustrates the difference of pressurized water versus air

 

Note how little 'reaction' there is when the tubing bursts.  If this was AIR...

 

 

 

[DennisThornton 4,769]

8 minutes ago, Jeff-C175 said:

They aren't doing AIR but WATER, this is interesting and illustrates the difference of pressurized water versus air

 

Note how little 'reaction' there is when the tubing bursts.  If this was AIR...

 

 

 

I've hydrostatically tested tanks and there's little danger when they burst.  Most of us have seen vids of tires blowing up and it's UGLY!  I've had them blow and thought it was a gun shot!

 

750 psi on pex huh?  Why use PVC?  My last plumbing job was all PEX and I'm guessing I've long ago done my last PVC supply job.  Might still use PEX for air though. 

[Jeff-C175 7,199]

3 minutes ago, DennisThornton said:

thought it was a gun shot!

 

Yep!  I keep my lawn cart behind the garage in the summer.  I was working in the garage one day and KABOOOOM!  I ran out with my flak jacket on to see who was firing shotgun behind my garage to find the cart overturned and one of the tires blown out.  And those are SMALL tires! 

 

Had those been filled with water if I even heard it at all, I might have thought the cart simply wet itself.

 

I was passing a semi on the interstate when it had a split rim blow out.  Lucky to escape with my life as the rim rocketed across in front of me and disappeared into the Kudzu.

[DennisThornton 4,769]

4 minutes ago, Jeff-C175 said:

I was passing a semi on the interstate when it had a split rim blow out.  Lucky to escape with my life as the rim rocketed across in front of me and disappeared into the Kudzu.

Oh my!  That's literally a take your head off ordeal!  Wow!  Scary for sure!

[Racinbob 11,045]

This is an interesting thread. I've re-plumbed two homes with PEX and I'm 100% sold on it for water. The first house I used an Apollo zone manifold and had each room on a zone. It had a mix of copper, PVC and iron pipe. This house had 100% CPVC The previous owner had the house built but did the plumbing himself. It was a sloppy job. I ran a 3/4" hot and cold main trunk the length of the house and branched off and installed a valve each device separately. In both cases I used the crimp connectors. In both cases zero leaks. In watching that video I really wouldn't be afraid to use PEX for air lines but, If I were to hard pipe a system I'd use either black or galv. iron pipe. 

[Jeff-C175 7,199]

44 minutes ago, wh500special said:

steam explosions

 

I believe that steam expands something like 17 times it's volume.  This is why one must NEVER EVER open the radiator cap on your vehicle when the engine is hot!  When that liquid above boiling temperature is returned to ambient pressure that liquid flashes to steam instantly!  That will melt your skin right off your bones!

 

I once accidentally opened my Espresso machine before the pressure was down.  Luckily I only burnt my hand a little bit but the cap got blown out of my hand and put a dent in the ceiling sheetrock.  It's one of the dozen or so stupid things I've done that my bride will never let me forget.  (there were many more, she just doesn't remember them all.  Ask her about the time I tried to smother a fire on the electric cooktop with a brown paper bag!)

Edited February 25, 2021 by Jeff-C175

[Jeff-C175 7,199]

43 minutes ago, DennisThornton said:

Might still use PEX for air though

 

I probably would too.  The only downside that I can see to it is that of the air retaining moisture and that is easy enough to remedy.  Heck, when I get a wild hair on my azz I might even beg the treasurer to spring for one of the RapidAir kits... AFTER she gets me my welder!

 

BTW, I'm not sure I believe the tech at RapidAir but he also stated that PEX is not as oil tolerant as their HDPE tubing.  Sounds like sales hype to me.

Edited February 25, 2021 by Jeff-C175

[DennisThornton 4,769]

13 minutes ago, Racinbob said:

This is an interesting thread. I've re-plumbed two homes with PEX and I'm 100% sold on it for water. The first house I used an Apollo zone manifold and had each room on a zone. It had a mix of copper, PVC and iron pipe. This house had 100% CPVC The previous owner had the house built but did the plumbing himself. It was a sloppy job. I ran a 3/4" hot and cold main trunk the length of the house and branched off and installed a valve each device separately. In both cases I used the crimp connectors. In both cases zero leaks. In watching that video I really wouldn't be afraid to use PEX for air lines but, If I were to hard pipe a system I'd use either black or galv. iron pipe. 

Yeah, PEX is great!  Bend it!  Snake it through studs, bend it around gently corners, cut and join in seconds, no heat, no fires no fumes!  Wonderful stuff!

And, if PEX is good for up to 750 lbs!  Why wouldn't it be good for air lines?  Indoors, out of the sun!  It's hard to think of every scenario that could possibly happen but for example, what if PEX and a little bit of oil are not friendly?  What if time played its role?  I STILL doubt that it would explode!  So what are we not thinking of?  Why have I read in more than one location NOT to use PEX for air lines?

[Jeff-C175 7,199]

5 minutes ago, DennisThornton said:

Why have I read in more than one location NOT to use PEX for air lines?

 

Because the internet is one big talking Parrot!  It repeats everything it hears, true or not, over and over, ad nauseum.  Just like me!  

[Zeek 2,286]

5 hours ago, Jeff-C175 said:

 

The difference is in the amount of STORED ENERGY.

 

Since water can't be compressed there is very little (to no) stored energy.

 

 

 

 

I'm sure you are likely correct about that and I get it, but we are only talking about 120-150 PSI in most cases which is still far below the rated pressures of PVC of 300+ PSI. So I'm still not

convinced it matters.

Edited February 25, 2021 by Zeek

[DennisThornton 4,769]

53 minutes ago, Zeek said:

 

I'm sure are likely correct about that and I get it, but we are only talking about 120-150 PSI in most cases which is still far below the rated pressures of PVC of 300+ PSI. So I'm still convinced it matters.

Yep, but when it does fail.  And perhaps that's the issue.  Or maybe it's after 20-30 years.  I don't know, but the pictures send chills up my back.

[squonk 41,038]

17 hours ago, Jeff-C175 said:

 

I believe that steam expands something like 17 times it's volume.  This is why one must NEVER EVER open the radiator cap on your vehicle when the engine is hot!  When that liquid above boiling temperature is returned to ambient pressure that liquid flashes to steam instantly!  That will melt your skin right off your bones!

 

I once accidentally opened my Espresso machine before the pressure was down.  Luckily I only burnt my hand a little bit but the cap got blown out of my hand and put a dent in the ceiling sheetrock.  It's one of the dozen or so stupid things I've done that my bride will never let me forget.  (there were many more, she just doesn't remember them all.  Ask her about the time I tried to smother a fire on the electric cooktop with a brown paper bag!)

Steam explosions. 

 

Working at the Hospital on a Saturday by myself. Boiler room is about 30' X 60'. 2 Cleaver Brooks 100 HP boilers running at 60 PSI. I am about 20 ft. from the exit door and about 10' from a boiler with my back to it. POW!!! The sight glass on the boiler near me explodes. Within 2 seconds the boiler room is full of steam, I can't see and have to feel my way to the exit and find the emergency shut off and get out of there. It was another 2 hours before the steam dissipated enough to go back in to find out what happened. Found parts of the sight glass all over the room in multiple directions.

 

I have been in more than one repair shop that cheapened out and ran plastic air lines. Leaks everywhere and looks like crap. You get a sag in it and water collects there until it's got a good puddle going you hit the trigger on an air gun and here it comes. I used to have to deal with pneumatic controls at said hospital. Had to run multiple air dryers and filters to keep the water out. Copper manifolds at the climate compressors with plastic lines teed into them running everywhere. You guys that want to run plastic, have at it.

Edited February 26, 2021 by squonk

[DennisThornton 4,769]

3 minutes ago, squonk said:

Steam explosions. 

 

Working at the Hospital on a Saturday by myself. Boiler room is about 30' X 60'. 2 Cleaver Brooks 100 HP boilers running at 60 PSI. I am about 20 ft. from the exit door and about 10' from a boiler with my back to it. POW!!! The sight glass on the boiler near me explodes. Within 2 seconds the boiler room is full of steam, I can't see and have to feel my way to the exit and find the emergency shut off and get out of there. It was another 2 hours before the steam dissipated enough to go back in to find out what happened. Found parts of the sight glass all over the room in multiple directions.

 

I have been in more than one repair shop that cheapened out and ran plastic air lines. Leaks everywhere and looks like crap. You get a sag in it and water collects there until it's got a good puddle going you hit the trigger on an air gun and here it comes. I used to have to deal with pneumatic controls at said hospital. Had to run multiple air dryers and filters to keep the water out. Copper manifolds at the climate compressors with plastic lines teed into them running everywhere. You guys that want to run plastic, have at it.

You have a point that I hadn't thought about, sags in the line collecting condensate.  I don't yet see that as a deal killer for PEX but rather something to watch while installing.  And PEX can be run to look wonderful too, just as good as anything else and in colors!

So far I think the biggest issue with non-metal air lines is moisture.  But before there is an air supply system, or perhaps I should say that many air supply systems start off with a compressor and a 50ft plastic or rubber air hose!  Anything, as long as it is safe, is an improvement.  Can always put a little filter/water separator at the end of the hose.  I used them at my paint gun even with my galvanized system.  No matter what, every system getting periods of heavy use should address moisture/condensate, which just might mean that they should have some metal somewhere!  So even if the PEX (or PVC...)  install is without sags, where's the condenser?  Need one somewhere if metal is not used.  OK!  Good points against plastic air lines.  ALL of them if there's humidity!  Plastic might be fine in Vegas!

 

You're underwear unharmed in that explosion?

[squonk 41,038]

Underwear was no where to be found. 

 

You need the hot air coming from the compressor to cool so it will condense. Nobody is going to run 500 ft of line until you get to your paint gun. That's why you need metal lines to cool the air and any  and all filters need to be away from the compressor. The only other way is to install a Refrigerated Dryer to get the air cool enough to condense. On medical air systems we ran multiple dryers to get the dewpoints down to about -20 Overkill for a shop but I was always fascinated at the steps taken to achieve that

Edited February 26, 2021 by squonk