PEX and Shark BIte fittings for LP air?

PEX is fine and so are shark bites, but shark bites are expensive. When I plumbed my shop for air I used high pressure (rated 150 psi) polyethylene tubing and plastic compression fittings (220 psi) from McMaster. The tubing is about 1/3 the cost of PEX and the fittings are a lot cheaper than shark bites. 5 years later it's still holding up fine.
 
One concern in using plastic for compressed air is what happens if the system ruptures. Unlike water under pressure, compressed gas expands as it depressurizes. Loose lines can whip around with possible serious consequences.
 
RJSakowski said:
One concern in using plastic for compressed air is what happens if the system ruptures. Unlike water under pressure, compressed gas expands as it depressurizes. Loose lines can whip around with possible serious consequences.
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That’s why you strap/clip the supply line down every so often, every couple feet would be or should be sufficient in most applications.

That’s also why I’d prefer using a metal compression type fitting over a plastic sleeved one....even in the gulf on boat landing pull stations we install nylon ferrules in the compression fittings and one can pull the poly flow line out of the fitting when jerked hard to esd the facility.....matter fact BSEE the gov regulator and inspectors look for that they don’t have metal ferrules because it just won’t pull through....

Plastic will compress then up n greater forces slide against plastic but will be bitten into by a metal ferrule until enough if possible force applied to actually stretch the tubing

I’m a Sr. Pneumatic Instrumentation And slow speed motor controls specialist in oil and gas facilities in the g.o.m.


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After considering pressures and volumes required and pricing everything out, I decided to go with 3/8 polyethylene tubing and plastic PEX fittings.

100 feet of tubing, all the fittings, clamps to tack the tubing to the beams, and two water separators - enough to do two drops in the basement, one by the machines, one in the hobby room for the airbrush - came to just under $100.

I did decide to add an additional regulator to the drop in the hobby room as I may need to adjust pressures for the airbrush and it'll save running up to the mudroom every time. Need to get some pieces-parts for that.
 
You'll soon find out that 3/8" tubing is not big enough for any volume, and the plastic fittings are the weak link.
 
I agree that 3/8 is on the small side. My (1/2 ID) plastic tubing and fittings have held up for 5 years of frequent pressurization and depressurization (I don't leave the compressor on all the time).

My plastic line never gets touched, though, it's up in the rafters and connects to 6" steel nipples everywhere there's a quick disconnect for tool hoses.
 
derf said:
You'll soon find out that 3/8" tubing is not big enough for any volume, and the plastic fittings are the weak link.
Click to expand...

For general use, I'd certainly agree with you. However, this line will only run a mister nozzle and perhaps an airbrush, so volume really isn't an issue. Also I plan to regulate the line to 50 psi max and more likely run it at 25 psi.
 
You could run the supply line to a storage cylinder in the shop and then distribute from there, that way you will limit the sudden pressure drop when you use air. A long supply line at 3/8 will drop supply pressure quite quickly with only a small demand, but storage cylinder will help prevent it being a problem.
 
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