Compressed air pipe selection

by george derr
(bassett, va 24055)

I have looked everywhere and I have been told that schedule 80 pvc pipoe should not be used. Why not? I intend to repipe my home garage soon and would like to know what pipe to use. I don't have access to a pipe threaded machine and the cost is a big consideration.







Bill says.... don't do it!!!!

Hi George.

While it appears as though PVC pipe has sufficient pressure rating for compressed air, that pressure rating is at a fairly low temperature.

When temperatures in the pipe environment get up into the 90's and perhaps even 100's, the pressure rating on PVC falls way below compressed air levels, and you may have a blow out.

The problem with PVC is that when it lets go, it doesn't just blow a hole, it shatters, and shards of plastic will go flying around the area like mini-bullets, doing a lot of damage to anything in the area, including people!

Since many home shops don't require the air flow of industrial compressed air applications, where big 3" and 4" black pipe are often used as air mains (that's not even a good idea) why not consider just using rubber air hose in your garage?

Buy good quality hose, and plumb your workshop just as if you were in a plant, with overhead mains, drop lines to your applications, etc.?

If it were me doing a hard compressed air plumbing job in my shop or garage, (and if I had the budget) I'd go for copper. I can cut it easily, sweat it together (no threading) and there's enough variety in copper fittings to move me from the copper to the couplers for my tools. Copper doesn't rust, a real plus for air systems which have a lot of water in them.

Or, you can even consider using 1/2" poly tube to plumb your shop, with 3/8" or 1/4" lines from the 1/2" "main" to the tools. While not as robust as the rubber hose, if the air lines aren't going to be driven or walked on, compressed air quality polyethylene tube works.

For more info, start reading this page, and follow the links to the other pages about plumbing compressed air applications.

Cheers, and thank you for writing in.

Bill

Comments for Compressed air pipe selection

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Mar 12, 2010
Go nylon
by: MEP1

Just a thought, but good nylon tubing has the same working pressures as most braid-reinforced rubber hose and is quite a lot cheaper. It's also easier to get a neat installation since it's a bit rigid and doesn't droop when strapped to a pipe or conduit. 1/2" OD nylon tubing has the same inside diameter of 3/8" hose, and there are fittings you can use where you just cut the tubing to length and push it into the fitting. They can be removed without tools as long as there is no pressure on it.
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Just triple check the pressure rating as the temperature rises. If the rating is suitable, go for it!

B.

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Copper piping - is it OK to use?

I am contemplating using 3/4" copper pipe instead of galvanized pipe in an small automotive shop. do you see any problem with using the copper?

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Bill says...

Using the copper, absolutely no problem as long as you can sweat fittings so they don't leak. There are lots of benefits to using copper...for example, copper doesn't rust.

I strongly suggest you do not use galvanized pipe for an air system. It wouldn't be too long before little pieces of the inner wall galvanizing came drifting down your air line with the compressed air.

Cheers,

Bill

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