Air lines-PEX


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Hello,

I have the chance to layout a 3,000sq. ft shop from the ground up. It's a blessing and a curse.  I am pricing out a "pre-made" air hose system-one of the "Blue" ones and the price is silly. Does anyone have any feelings or thoughts on using 3/4" PEX tubing for the main line and the drops? Using PEX I would be able to create a ring main and add more drops for a 1/4" of the price of the "Blue" systems. PEX is better than PVC, but is it good to go?

 

Thanks,

Jeff

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I wouldn't.    Do a Google search for:   "pex for compressed air".    Always good stuff on such topics at the GarageJournal forums.   I'm sure that will come up in such a search.

No need to go over it for the multi thousandth time here.

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PEX is typically HDPE, the same material that milk jugs are made out of. Under pressure it stretches and moves A LOT. It also moves a lot with temperature changes. I've seen water lines shrink probably 20 feet after sitting in the 80 degree sun to being installed in the ground. I don't know the max pressure that the lines can hold but i know the big HDPE water lines that are installed are only designed to hold 150 psi and not much over that causes bursts. Is there anything wrong with PVC? PVC can be solvent welded so no special tools and the bends and fittings might even be cheaper.

Just looked it up pex is rated for 160 psi @ 70 degrees and drops to 80 psi at 100 degrees. If you shop is unconditioned you are more than likely going to over pressure and cause bursting.

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I've never heard of anything positive about PVC. Yes, it's easy to install, duck and cover when it fails. It's a bomb when it lets go.

I'm installing PEX inside, in the free air. The temp changes won't be extreme. I don't doubt that there is movement in PEX, but I can factor that in with "slack" in the system.  I like PEX just for the fact that it moves where PVC is fixed and can blow.

I'm "only" going to have 125psi on the system.

 

Thanks,

J

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My problem with plastic is that it's almost impossible not to have a sag in it, here and there.   If you have a refrigerated dryer before the lines, it probably won't be much of a problem, but moisture will be in there otherwise.  Anywhere there is a sag in the line, it will accumulate water, and some of it will come along with any air you use out of the system.   I'd use metal, and do it once.  Metal can actually help get rid of water in the system, if you install it to do so.

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Thanks, Tom!

I live in AZ so water isn't a huge problem for me. I do plan on building a "radiator" between the compressor and where the air reaches the "field" and then install a water trap. 

I used to drain my compressor twice a day in Maine, but I never get water in AZ.

 

Thanks for all the feed back!

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I know pvc fails that way but it's burst pressure is considerable higher than HDPE. Sch 40 PVC burst for 3/4" is near 2,000 psi if it's a huge concern Sch 80 is closer to 3,000. SDR pvc isn't designed for pressure use and is probably why you think PVC is unsafe or not suitable.

I'd agree with tom though if your building a 3,000 sq ft shop don't cheap on your tubing do it metal do it once and be done with it.

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The problem with PVC is that, even though it's stronger than PEX, it will explode if there is a weak spot or if it takes a bad hit from something. I almost behaves like glass in a situation like that. And if it is cold it doesn't take much of a hit at all to break it.

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PVC sales talks air down. https://www.pvcfittingsonline.com/resource-center/using-pvc-pipe-for-compressed-air/

AS for PEX, not all PEX is identical. Not only, but the high end of the pressure rating goes down as temps go up. Add to this that the maximum rating is less than half of that for hoses...which are a wear item. Just thoughts. Metal pipe is so cheap and has reliable shortcomings, none of which are pressure. 

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31 minutes ago, Chestnut said:

Crap sorry for brining up PVC clipboard warriors attack!

We tried it. Failed in less than a week. I think material from box stores gets beaten up. It seems like a good idea. Just haven’t seen it work out well all that often. 

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Not Air related but PEX temperature related response....

We live in Florida - we have a tankless water heater.

There is about 4' of PEX installed on the outside by the RINNAI and the entire first floor was replumbed with PEX as well.

Our outside temps have hit well over 100 degrees in summer and our internal temperature recently hit a low of 20

We've had no issues what so ever with PEX cracking or breaking or splitting

We've had this system for 3 years now

Just and FYI

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1 hour ago, new2woodwrk said:

Not Air related but PEX temperature related response....

We live in Florida - we have a tankless water heater.

There is about 4' of PEX installed on the outside by the RINNAI and the entire first floor was replumbed with PEX as well.

Our outside temps have hit well over 100 degrees in summer and our internal temperature recently hit a low of 20

We've had no issues what so ever with PEX cracking or breaking or splitting

We've had this system for 3 years now

Just and FYI

Water pressure is typically sub 60. That has to be regulated or you lose things like toilet valves prematurely to cavitation. Air molecules are also smaller than water molecules. There is just not a good apples to apples comparison there. I am not anti PEX. I use it extensively. I just am reporting manufacturers specs. Do what you want. Just know I would recommend against it for air. Should you chose to, check back in with any ups or downs so we can all at least track one experience. 

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35 minutes ago, C Shaffer said:

Water pressure is typically sub 60. That has to be regulated or you lose things like toilet valves prematurely to cavitation. Air molecules are also smaller than water molecules. There is just not a good apples to apples comparison there. I am not anti PEX. I use it extensively. I just am reporting manufacturers specs. Do what you want. Just know I would recommend against it for air. Should you chose to, check back in with any ups or downs so we can all at least track one experience. 

Do you see a lot of PRVs? The systems that I've been working on are in the 80-110 psi at the main at least.

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Wow that's nothing. Getting fireflow in developments must be a pain in the arse. It's fairly flat here as well still have a lot more pressure for some reason at least in the 5 systems I've dealt with so far. I want to say during the inspection on my house the guy said it was around 60ish measured on our top floor. I started thinking about it when it was mentioned the poorer performance that pex has with temperature. And some areas i know the houses are getting dang close to over pressurizing the pipes from water heaters.

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I can't address PEX or PVC but can tell you in 14 years I have never had a compressed air issue in my shop. The system is run throughout the 16 x 36 shop 5 drops, about 120' of copper pipe, all drops have ball valve/pressure regulator/ and water separators. Probably one of the cheapest things I have done in my shop.

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Hey,

Been busy....I am not going to use PVC-period.  I have decided to use 1" PEX-AL-PEX. It is basically the same thing as the "blue" hose being sold as a kit. I'm not worried about sunlight, it's inside, not worried about the pressure-the PEX-AL-PEX is rated higher than reg PEX. 

Plenty of youtube videos showing the regular 3/4" PEX being pressured up to 900+ PSI before it lets go. 

I will let everyone know how the install goes, when it happens. 

 

Thanks for all the feedback!

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I bought some 3/4" for an under floor heating system a couple of years ago, from this place:

https://www.pexuniverse.com/pex-pipe            85 cents a floor with free shipping seems pretty good for 1", but I haven't really shopped for it.               I don't have a 1" tool.   Let us know what crimping tool you end up with.   I haven't looked a PEX crimpers for years.

 

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I have a small tool for 1/2 and 3/4 that's just two small blocks of steel with two bolts and nuts.  It's made for getting into tight spots, which it's good for, but it's a lot cheaper than the big crimpers.  If they make one of those for 1", it wouldn't be too bad for one job.  You can use an impact driver.

edited to add:   I looked and couldn't find one.

This one doesn't seem too bad.   Buy it, do your job with it, and I'll pay you half the purchase price plus shipping for it.   I don't know if I'll ever need it or not, but won't mind having it in one of my plumbing tool boxes.

https://www.amazon.com/dp/B019BYLBDA/ref=asc_df_B019BYLBDA5345359/?tag=hyprod-20&creative=395033&creativeASIN=B019BYLBDA&linkCode=df0&hvadid=167152075853&hvpos=1o7&hvnetw=g&hvrand=1686543734362670726&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9010246&hvtargid=pla-307642927918

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On 1/16/2018 at 9:42 AM, Jeffm510 said:

I do plan on building a "radiator" between the compressor and where the air reaches the "field" and then install a water trap.

If you are going to do this ^ then you should just use black pipe or copper.

There is a brand name of RapidAir out there which has a few different types of flexible tubing for compressed air. Looks like they have a nylon tube they market for home garage installs. Its only 1/2" though.

http://www.rapidairproducts.com/

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