I have avoided getting myself involved in these PVC air line debates for several reasons, namely the name calling and heated arguments that always seem to follow when people have strong opinions one way or the other. Also I am somewhat guilty myself because I have made several potato guns out of PVC and in addition to a compression wave, you also have heat thrown into the mix which can really spell disaster. I also considered running PVC airlines in my old shop but went with coiled air hose instead. Lurking on the Garage Journal when I was building my current shop steered me away from PVC almost immediately.
So here is my thoughts on PVC air lines (some of my comments are paraphrased from other websites): First, don't do it and if you do (or did) at least bury it in a wall so if it does blow the shrapnel is safely contained. Any fittings or adapters ought to also be buried in the wall so that only a black iron pipe is expose in the shop environment. I suppose burying the line under ground would be safe as long as all the fittings are buried as well...
I guess you need to look at it this way, pressure is pressure. If a piece of pipe is rated for 200 psi, it can handle 200 psi, whether it's water, air, or any other fluid. The difference between air and water is that water is not compressible. In fact, SCUBA tanks and other high-pressure tanks are routinely "Hydro tested," which involves filling the vessel with water, then pressurizing it to the working pressure. Typically, a dye is added, so leaks can be easily found. That, however, is not the primary reason for using an non-compressible fluid - since it cannot compress, it does not expand when depressurized. That means that if the pipe was to fail, it would just crack or pop, rather than exploding violently. The reason PVC pipe is not considered safe for compressed air by OSHA is that in an industrial environment, air lines can be subjected to unusual forces, such as sudden blows, drops, or sharp bends, which create weak points in the plastic's structure. These weak points eventually become failure points, which are the causes of explosions when operating within the maximum pressure rating of the pipe.
PVC is also not treated to be resistant to ultraviolet radiation and will degrade if exposed via a window or even florescent shop lighting. PVC that has degraded becomes even more brittle. I bet more than one of you has accidentally busted a sewer vent cap with your push mower. That cap broke because it was sitting in the sun for many years becoming more and more brittle.
Here is a first hand account that I shamelessly stole off another website:
My neighbor had 3/4" Sch.40 PVC he had been using as compressed air lines in his garage for 15 years operating at 125 psi max pressure. He recently upgraded the compressor to a Wayne series 5000 which is rated for 175 psi. I told my neighbor to not even attempt and use his existing air lines if he's going to pump up his 80 gallon tank and air lines to 175 psi. Well.......he didn't listen. As soon as the pressure got up to about 170 psi, he stated the air line fractured and sent PVC shrapnel flying. He stated it sounded lke a gun going off! Fortunately, no one was injured but a wise lesson was learned. Aftwards, he told me he should have listened......duh!
Here is another first hand account, also stolen:
PVC is bad.
Here's a shot of a line that came apart at a shop I was working at:
One more stolen story:
Air Line Caused Explosion - 06.27.2007
On Wednesday June 27, 2007, the Monroe Fire Department was alerted for an explosion in the 100 block of west 8th Street. Upon arrival, Fire Command found employees outside of the building and stating that something exploded inside of the building. Once inside, there was damage to the ceiling and PVC piping on the floor. Crews secured the building and utilities. Maintenance personnel stated that the pipe was connected to the air compressor. During the investigation, it was determined that a elbow connected to the pipe released causing the explosion. There was no structural damage to the building. Maintenance personnel were inside fixing the piping and were expected to back up and running by the morning,
Green County EMS, Monroe Police Department, Wisconsin State Patrol and Monroe Building Inspector assisted at the incident. Crews remained on scene for 1 hour.
And here are my potato guns!
This is the Mark 1. It will easily shoot a russet over 100 yards!
This is one that I never finished painting the desert camo. It is an over the shoulder rocket launcher style.
