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I have 1/2" PVC ran from my compressor to a hose real hanging on my ceiling. It works well, but I would like to add a PVC union around the last bend just before the reel.

Would the union be tight enough to not leak air out?

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PVC is not rated for and not safe for compressed air service, with the limited exceptions of "if buried in the ground or completely screened in wire mesh to catch the shards."

It makes lovely shrapnel - it has injured people. Nice and cheap until it costs you something more dear than money.

Here's a 480 PSI (water, not air - no PVC is made or rated for air service) that worked for 15 years and expired at 175 PSI (air) or less. Shattered pipe

Link for the above picture. The writer of the link may have "learned" the wrong lesson - even at lower pressures, the pipe degrades and fatigues in air service, and fails in a fashion that is dangerous.

An OSHA link from 1988.

A pipe manufacturer page

Some more reading/experiences/etc...

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Interesting, I've never heard that. If you know, what does it make a difference what's flowing through the pipe; pressure is pressure right? Or is it maybe because air has more drag, which wears the pipe down? – Gary Jan 8 '14 at 5:43
Less prone to crack in the first place with water, I think. The big difference (read the links for more detail) is that air (or any gas) is a compressible fluid, while water or most any liquid is incompressible - if a pipe carrying 1500PSI water cracks, a little water leaks out and the pressure drops to nothing - no energy is stored. A pipe carrying 150PSI air cracks, and the contents of the pipe immediately expand to 9 times their former volume, propelling shards in front of them. – Ecnerwal Jan 8 '14 at 14:54
The amount of energy released when compressed fluid is decompressed will be proportional to the pressure and the amount by which the volume will increase at atmospheric pressure. For liquids, that's a much smaller value than for gases. – supercat Nov 15 '14 at 20:59
This is a safety issue, if this was a working shop, OSHA would shut you down because of the safety hazard. It rates up there, not quite as high as "don't run acetylene through copper". – Fiasco Labs Nov 15 '14 at 23:48

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