Compressor air supply line

[Jim Young]

Went to the hardware store today and was looking for materials to plan out my air compressor plumbing.

First question: Can I use PVC for the air? I looked at the 3/4" stuff and it said it was good to 460psi. I keep thinking this stuff might shatter when hit. It was way cheaper than equivalent size copper. Also looks alot easier to install.

Second question: Was size tubing should I use? It seems that all the connectors are 1/4", why run 3/4" pipes? My original though was to run 3/4" pipe for a main truck and then branch out to 1/2".

My compressor is a 7 HP two stage 135psi unit.

[Steven Wilson]

Use the search function. Don't use PVC for air, those PSI ratings are for fluids not gasses - big, big, difference.

[Joe Pelonio]

I used 1/2", and agree, PVC can blow out on you. There is plastic pipe made for air.

[Bart Leetch]

Standard copper used for water is ok.

[Randal Stevenson]

If this was in a commercial shop, you could be fined by OSHA for using hard pvc for airlines. However cheaper air hoses are made partially of PVC, which is why I believe people seem to think they should be able to use it.

There is airline made of ABS plastic, under several brand names, it is color coded differently then DWV. You will find that it makes black iron or copper look cheap.

The reason for bigger tubing, is it acts as a second tank. While the connectors are smaller, they act as a door, to allow so much air out. Like water line, it is better to have bigger lines to an area, in case of using multiple items (nailer while someone is filling a tire).

[Kyle Kraft]

Steve gives some good advice. OSHA frowns on pvc air lines, and every time I see them in someones shop I cringe. Use copper or black pipe, it's not that hard to install. Rise above your fears and learn a new technique like pipe threading or sweat soldering.

[Jim Becker]

Type L and/or K copper. Or black pipe. Never PVC. It's not rated for compressed gases and as eluded to, it can be quite brittle and shatter if accidentally struck. (There has been a lot of dialog about this over time in this and every other forum...) I used copper for my lines and have been very pleased.

[David G Baker]

PVC used for air lines has been used for years and people that use it swear by it until it explodes sending chunks of plastic all over the place. This topic has been discussed in several of the forums that I belong to and the general consensus is that it is a very bad idea. It is cheap and easy to work with but a bomb waiting to blow.
Black iron pipe or the heavier walled copper pipe are the two most recommended but there is a PEX type tubing designed for pressurized air but I do not know what it costs or where to buy it.
If you plan ahead on the threaded pipe you will be able to purchase most of your smaller lengths pre threaded where you purchase the pipe so you won't have to invest a bunch of money in tools to do the threading.
As far as sweating copper pipe goes there are many sites on the Internet that will help you with the basics and once you do a little practicing it become easy. (been there done that) The heavier walled copper pipe is a little more difficult to insert into the standard fittings than the thinner stuff.

[Jim Young]

Alright, you convinced me, I'm going with copper. I did already scope out the thick walled stuff at the big box. Today will be measuring day.

[Kurt Strandberg]

I ran 1" fire sprinkler pipe and 1" X 1" X ½" tees and 1" X ½" 90's at the ends and the bushed the ½" down to ¼" for the air fittings, I used the air hose that came with the compressor and connected that to a tee in the pipe with a valve out the bottom to collect moisture and I go up through the ceiling in the corner of the polebarn and come back down through the ceiling in the center of the polebarn into another tee, out the side of the tee to other openings and out the bottom of the tee to another valve for moisture

[Jim Becker]

Jim, don't forget to provision for a water/moisture filter and remember that your actual connection from the hard lines to your compressor is best to be done with a very short flex hose to isolate vibration, etc. Be sure to bring your compressor's drain out so it's easy to access...some 1/4" NPT and a ball valve are easy to provision for that.

[Brian Elfert]

Back before I decided to sell my house and move somewhere I can build a real shop I started to run 3/4" PEX for my air lines.

PEX is rated for something like 180 PSI. I never actually aired up the system before I tore it all out to finish my basement before selling the house. If PEX fails it should simply split and not shatter like PVC.

[Jim Becker]

Brian, PEX, like PVC, is rated for liquids, not compressed gases, but it certainly would be "safer" in the sense of shattering and shards. There is a similar product available on the market specifically for compressed air systems...it's been mentioned in one or more of the many threads on this subject.

[Matt Meiser]

One tip on sweating copper is to use MAPP gas instead of standard propane. I've always struggled sweating copper--I could get the job done eventually, but it wasn't unusual for me to have to resweat stuff. I recently bought a cylinder of MAPP gas and did some manifolds for where I transitioned from copper to PEX for my bathroom. What a difference. The MAPP gas heats the joints much more quickly and thoroughly. Other than that, clean (those wire brushes made for it are great) and flux and you should be good.

I did my shop in copper (back in the "old days" about 4 years ago when it was cheap.) I'm very happy with it other than a pinhole leak at one joint I've never gotten around to fixing. That's just a matter of resweating that joint but since it is small enough that it takes about 12 hours for the piping to leak down when the valve between the compressor and the lines is closed, it hasn't been high on my list. I did everything design-wise by the book:
- my trunk line slopes down, away from the compressor
- at the end of the line there is a drip leg with a drain at the bottom
- each of the drops is plumbed off the trunk line with a T that points stright up, then has 2 90's to turn it back around toward the ground. This keeps water out of the drop.
- Each drop also has a drip leg with a valve for releasing water.
- Each drop has a valve before the filter/regulator that allows me to shut it off to service the filter/regulator (not that I ever have )

Harbor Freight sells some 1/2" NPT 1/4 turn ball valves and puts them on sale dirt cheap on a regular basis. Before the anti-HF crowd jumps all over that, I've had them for 4 years with no issues When I bought them I think I paid $2 each for them. And if you look at the ones at Lowes, they are made in China too (at least the ones I looked at before going to Harbor Freight.)

For the compressor connection, I bought a hydraulic hose assembly from Tractor Supply. I figured that if a hose can withstand pressures in a hydraulic system, air pressure should be a piece of cake.

[Matt Meiser]

The think I'd worry about with any flexible product like Pex would be a whipping effect if a line broke. I've seen that happen with a rubber air hose more than once and its kind of scary. Air hose would hurt like you-know-what if it hit you--PEX is just hard enough I would think you could get a nasty cut.

PEX is awesome to work with though. I did all the PEX in my bathroom in less than an hour with 0 rework required. The pipe is cheap but the fittings are pretty expensive. You probably need a fair number fewer fittings since you can bend PEX, so its still probably cheaper. I would think it has to be cheaper labor-wise if you have it done. You only need a utility knife and the crimper to make the connections and you don't have to worry about catching anything on fire. If I was to build or completely replumb a house I would go PEX, with all the lines going back to a central manifold like they do on This Old House.