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I'm planning on plumbing my shop for compressed air and I think I want to use nylon tubing, like what comes in the RapidAir kits. I don't want to use PVC for obvious reasons, and though I think PEX could technically work, its temeperature derating curve concerns me given the pressures and temperatures the material would see.

My question is this: has anyone ever used PEX barbed fittings and crimp rings with nylon tube? I'm not a fan of push-to-connect fittings and compression fittings are expensive and difficult to install in tight spaces. I'm sure brass PEX fittings could handle at least 160 psi (what I believe is PEX's maximum rating) and I think the dimensions are compatible with nylon tubing. What do you think? Thanks!

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  • What "obvious reasons"? If PVC isn't suitable, why did you mention it? – isherwood Mar 6 '19 at 14:07
  • PVC shatters when it fails under pressure, so it's supposedly quite dangerous. I mentioned it because it usually comes up in conversations about shop air systems with non-metallic pipe. – John Mar 7 '19 at 4:08
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There is a great video on YouTube by "The Build Show" about various PEX and push to connect fittings. They pump them up until they burst. They burst well above the stated ratings. Unfortunately I can't answer the nylon pipe question but check out the video

The Build Show with Matt Risinger 14,000 PSI test

I temporarily installed PEX Airlines and PEX oil line for my best friend who is a mechanic and that was four years ago.

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  • Thanks! I've actually seen that video and I've been considering recreating the experiment with nylon/PEX fittings using lower pressures. – John Mar 7 '19 at 4:27
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Pex will work as long as you dont exceed the max PSI. Moisture build up will be the problem. All of the built up moisture could escape into your air tools.

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  • Yeah, I'm not terribly concerned about the moisture. Each drop will have a drain valve and I'll use an inline filter at the compressor... maybe a dessicant too. I'm more concerned about the temperature. The air lines will run in my attic, where it can reach 150-160 degrees F. PEX's derating factor at that temperature is 0.7, meaning you shouldn't give it more than about 110 psi--I'm not sure I can say I'll do that. For that reason, I'd prefer to use nylon. I believe DOT nylon air brake tubing is rated for use at its maximum pressure up to 200 degrees F. – John Feb 4 '19 at 2:34
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Short answer: NO

Nylon doesn't compress the same way PEX does and thus needs to be compressed more so your go no-go tool won't be able to tell you if you have a good fit.

Long Answer: GAWD NO!

Your fears are totally unfounded, those push-to-connect fittings are far more secure than PEX crimp fittings - Porsche, Ferrari, Jaguar, Mercedes, BMW, Fiat and Volvo even use them in their cars. They only fail if you don't push the tube in far enough. Crimp, or threaded fittings fail in all sorts of unexpected circumstances.

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    Nylon is actually more dense than PEX (>1.2 g/mL vs. 0.9-1.0 g/mL). Still, you could have a point. Nylon's Young's modulus is approximately four times greater than PEX's, so it would take more force to deform it equally. – John Mar 7 '19 at 4:26
  • Yea - I figured I had about a 50-50 chance of being correct on that; I remember there was a difference from putting in a refrigerator line, just couldn't remember which way - anyway - updated my answer so it would be more correct. – virtualxtc Mar 8 '19 at 8:33

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