SpudFiles

While I have never used CO2, I hear that the main problem for using it with PVC is that it gets cold upon expansion. For obvious reasons, this is dangerous for PVC. However, people who paintball, etc. use mostly CO2, and like to make their own guns (If they're from here ). I couldn't sleep last night, and my mind wandered to an episode of Smash Lab I saw. The show isn't very good, but I got an idea. In the show, they demonstrate how the cold of expanding gas can be offset by the (venturi effect?) bringing in warm atmospheric air. They showed an emergency airplane escape slide inflating, and how the airstream pulled in air from the atmosphere to keep the flowing gasses warm. I wondered if the same idea could be used in a CO2 fill mechanism. The setup would be: CO2 tank->hose->tee with check valve that only allows air INTO the tee, from the atmosphere-> more hose, and finally the reservoir, regulator, etc. I don't know if this would be possible, let alone practical, as I have no experience with CO2. Thoughts are welcome.

Long winded explanation, huh

If you use a proper regulator, such as Palmer's, this is not necessary. Other than that, I wouldn't recommend using CO2 and PVC together without a regulator.

It sounds kind of like a vortex tube

Like you said, the CO2 in gas form isn't cold in itself; it's the expansion as it goes from liquid to gas that makes everything so damn cold. A good reg will take care of this, but something else that I'm surprised doesn't get mentioned around here more, is an anti-siphon tube.

Basically these are nothing more than a curved tube attached to the pin valve inside the CO2 tank, ensuring that only CO2 in gas form will leave the tank. There's a good description at this site here http://www.madpaintballer.com/co2-anti-siphon.php. Otherwise, if your tank is mounted vertically, this is not an issue. Or you could run a remote line, which usually gives plenty of volume for the gasses to expand before they get to the regulator/chamber.

A good reg is still always essential, but you still gotta keep the liquid out somehow.