Air compressor and PVC pipe

[JBailey]

I would like to plumb my shop to route air from my compressor to strategic locations. Never having worked with copper, I am considering using PVC pipe. Only problem, the instructions that came with my compressor explicitly states "don't use PVC". Anybody ever done this? Is it really unsafe?

[John G]

My Dad used PVC in his machine shop. He did a hydraulic test and found it to be good for several thousand PSI liquid. He never had any trouble with it.

I understand the issue is breakage. If you happen to hit the PVC with a blunt object, it could break or shatter. I would not use PVC. Copper is very easy to work with. That would be my choice.

John

[MoRo]

It's perfectly safe......if you only run 40 psi in your airsystem. But, of course, you'll be running 100+ psi, just like the rest of us do. PVC won't take that pressure and it'll blow apart........somewhere, usually in the vicinity of where your head is at, thence the safety warnings. You could investigate C-900 PVC, but it's gonna be a heckuva lot more spendy than copper. You could also use steel pipe which you can just thread together with tees wherever you want a take-off. I'd prefer that to copper, even.

[Andrew Mackey]

Dangers of using PVC - 1) It gets brittle with age and cold - could lead to catastrophic failure. 2) It will not tolerate movement over 60+ PSI - you must secure the attachment points so that there is NO movement at all where the hose fitting adapters are attached, and you must use a vibration isolater at the compressor, to stop vibrations generated by the compressor from affecting the pipe. 3) Heat generated by compressing the air will soften the pipe, leading to stress failure (hence the warning on the compressor) 4) any oil contamination (oil getting by rings in compressor) will cause catastrophic failure - PVC will not tolerate hydrocarbon contamination. PVC must be supported every 5 feet, copper 8 feet.
If you use copper, you can solder the joints - positive connections! If you Don't know how to solder, and can't get someone to show you, you can use compression fittings. I recommend using 3/4" Type L Copper, sweat fittings, reducing at your connection stations to 3/8" IPS for your connection points. Put ball type valves at all drop points, so if a coupler goes bad (and they do!), you can replace it without dumping the entire air system.
Andrew

[Nork]

Here in the Netherlands PVC is used in industrial settings BUT,
Only larger heavy spatial impact resistant version.
This does of course have its cost.
What you can do is use pressure hose (the one with a fiber strengthening).
This works pretty well too and is cost efficient.
I have 1 that’s over 20 yards so it gives you some freedom.

Nork

[spfx_dude]

I havd used PVC and it is rated to 300 psi depending on the diameter. I think you are talking water pipe as opposed to electrical conduit. Others are correct that PVC does not handle vibration, cold temprature, or fracture well, but then some of that is applicable to metals as well. I think you can also get schedule 80 PVC....

I am currently rigging my shop with 3/4 schedule 40 black pipe, because I have lots of it hanging around from an old project. It will also serve as additional pressure vessle. I will be adding ball valves at each branch for shut down incase of problems.

Spfx_dude

[Robert H. Thompson]

Don't use PVC pipe! I watched my neighbor blow the siding off his shop when the PVC pipe blew up. Use steel water pipe. Bob

[Phillip Hutchinson]

G'DAY
We use and sell black nylex tube at work its specificly made for air lines,
you don't even use a spanner to connect the hoses to the fittings just push them in.if you need to take one apart you simply push in the ring on the end and out it comes,if memeory serves me right the fittings are made by LEGRIS. THESES THINGS ARE THE BEST THING SINCE BUTTON UP BOOTS
REGARDS PHILLIP

[Larry Rusch]

The problem with PVC and CPVC is when it fails, it shatters and sends very sharp shards in all directions, much like exploding glass. It doesn't have to be old or cold for this to happen either. That's why it's only approved for liquid service. Plastic pipe specifically made for air service won't do this and the pipe and fittings are made to a different size standard than PVC (IPS) so one doesn't inadvertently mix PVC fittings in when installing air lines.

[EDWARD COLE]

Well fellers I sure would use sch. 40 metal water pipe .quite simple to assemble . Must seal the threads well . be sure to put in some union fittings so to take it apart . When I added on to my service shop I plumbed it over head and in the walls . With the hose couplers sticking out threw the dry wall . All so I just finished the son in law s new shop the same way .. P V C would be simpler but I wouldnt trust it . I have had those coil up hoses blow up , they throw peices ever where . Sure do hurt when they hit you ..The cheep hoses are very {dangerous} ED .

[Forrest A]

I've always seen black/gas pipe (which I believe is up to code in the US) used for transporting air under pressure. I would steer clear of using PVC for the gernade effect when it does let loose. The steel pipe is cheap, I think I paid $6 US for 12 feet of 1/2 inch. Fittings are where the money starts to pile up. PVC costs aren't any better.

Forrest A

[John Newman, Jr.]

I strongly agree with the iron pipe. One reason you should use black pipe is that if you use galvanized, there is some risk that it can flake off and possibly cause a problem in tools, regulators, etc. Always provide a drip leg with a draincock at any outlets you install to catch moisture & debris (and to be able to purge same)

[oldtool53]

Hi , we plumbed part of our shop air system with PVC. DO NOT USE IT !!! We have since replaced most of it with black iron pipe. When it breaks, it explodes and sends pieces of PVC flying in all directions.

Have a nice day,
Mark (oldtool53)

[KidDynamo]

I'd skip the black iron and used galvanized. That is what I use on ship's air systems and they MUST work.

I'll grant that black won't cause most people much problem but it will rust inside, to a degree. I sure wouldn't use black for air for one of my customers.

Use black, if you must, and if you get it free, but use new galvanized for new work, if you can. Schedule 40 for under 125psi, only.

Copper tubing works good for similar pressures on small stuff like gauge lines, controls, pressure switches, and stuff that doesn't require much volume. Flare fittings and ferrule fittings, amongst others work fine.

I don't use pvc for any air stuff, but sometimes plumb some of the saltwater sanitary system with pvc because it doesn't corrode.

[Forrest A]

I would think that after seeing gas pipe (black) used in so many places for compressed air, natural gas is loaded with moisture too by the way, that rust would be a bigger problem than it is.

I can understand the use of "Galvanized" pipe on a ship used on salty seawater to be an advantage but have not had any "rust" related problems with my air line set-up in my house.

In either case a filter can be installed on the end of the air line for air tools to protect them from rust and flaking off rust proofing compounds.

As for PVC on sewage lines, I hope you aren't pressurising them. I wouldn't want to be on a boat with PVC lines pressurised with loads of waste inside

Forrest A

[HoMade]

Natural gas may be loaded with moisture, but it's not loaded with oxygen - no rust.

However, I would worry more about black pipe in an very humid location. I worked in a shop in Michigan that used black pipe in a system at least 15 years old and even in the paint booth, rust was never a problem. Seems you would be fine if you put a water trap close to the compressor, but most setups I have worked with placed the traps out by the outlets.

[Clark Bigger]

the shop I work at ran pvc and copper pipe from 1967 untill 2002
no big explosions we run 200 psi
we made an air dryer in 1986.... manifold type ...hanging on the out side of the shop that elimanated 90% of the water from the system
new owners had all replaced with black iron I have alot of particles in the system now...messes up air solonoids an such
I feel that PVC and copper are OK

[John Hanson]

I had a boss that plumbed his shop with PVC (sched 80) and it worked for a while....then it blew one day...luckily we were at lunch. It sent razor sharp arrows of PVC through 2 airplanes.... so in the end, it cost him THOUSANDS of dollars in repairs. It was supported every 5 feet, and all the corners were double supported. The system ran at 120psi, and had a 6 foot long vibration isolating hose between the compressor and the PVC. The insurance company not only wouldn't pay for the damages, but cancelled ALL his insurance at once!
I wont work in a shop with that stuff used for anything but water!!
JH

[Mike Dennis]

Pressure Piping Code requires black pipe for a reason. Use what is legal and chances are, if installed correctly, it will be safe!!

In some juisdictions "L" or "K" copper is acceptable (not "M" such as water pipe), hard or soft. Flare fittings are OK but NOT compression. Silver solder is acceptable where copper is allowed, such as Dynaflow, 6% or 15% Silfos. For an inspected job you have to be a certified brazer but in most jurisdictions it is not enforced for small, home jobs. Takes at least a MAPP gas torch for silver while oxy/acetelene is much better.

PVC & CPVC is NOT acceptable. I am sure there are some specialized plastics that ARE acceptable - but certainly not the stuff we use for water!

For drops to service points, take off the TOP of the main and use two elbows to attach to the down pipe. Make sure the main is pitched back to the compressor to let the water run back into the tank to get rid of it. When it is not practical to pitch toward the compressor tank, pitch it toward some other collection / removal point that will be drained often. NEVER run pipe level!! Each verticle drop pipe should have a tee to serve the coupler or regulator from the branch of said tee and a nipple and cap at the bottom for dirt / moisture. Even better is a valve to drain the dirt trap. The more pipe exposed the better as moisture removal will be aided. When the air is cooled, water condenses out and can be drained. It is impossible to have too many drain points!

Schedule 40 black pipe is suitable for shop air. Couplings, tees and elbows MUST be of the beaded type. The straight couplings that come on a length of pipe are thread protectors or conduit couplings. They are illegal on gas or pressure. Throw them in the trash. Reason is they are threaded straight through; not tapered. Very often they will leak. They also take up too far on assembly messing with your length calculations. Cast iron fittings rather than malleable are NOT acceptable on air! All -thread nipples are forbidden as are bushings; use reducing couplings, reducing tees and reducing elbows instead. Street elbows are acceptable but discouraged. The number of unions used should ONLY be as many as required to assemble the system - no more. The only time a coupling is permitted in a run of pipe less than 21 feet in length is when it is impossible to assemble otherwise. In other words, if you need a 10' run of pipe DO NOT make it up of two 4' pipes and a 2' pipe with 2 couplings! Folks who do that will not pass inspection and are derisevly known as "nipple plumbers".

Ball valves are good but buy decent ones with an adequate pressure rating such as 200 WOG. Avoid stop, plug and gate valves. Beware cheap imported valves. Some are, of course, OK. However, many will not stand the pressure and can fail in a rather spectacular manner. Those that do NOT have an adjustable packing gland on the stem are usally junk and in my area will fail inspection. I once used some Italian valves that I had to remove at considerable expense. The threads were not cut correctly so the pipe bottomed out before they sealed. SInce that fiasco I have been more picky about valve quality. Apollo / Conbraco valves are excellent. Some Watts and Hammond are OK while the cheaper grade is junk. Beware any cheap valve!

No doubt some variations of the above exist in different areas but for my area that is what will pass inspection.

[Andre Blanchard]

The shop I work in just replaced PVC with this stuff.
http://www.garage-pak.com/compressed...ipe/index.html

Every month or so the PVC would let go a joint someplace, big bang, lights getting knocked down, etc..

The aluminum pipe is not that bad for cost, the fittings are a bit expensive but it is very fast to install and make changes to.