SpudFiles

I've seen on the internet that people have used this valve apparently without any modifications. Could someone please tell me how sprinkler valves work, if this one would work and if it would require any modding. The model is a Orbit 1 In. FPT Anti-Siphon Valve incase the link does not work.

http://orbitonline.com/products/Valves/02/16/07/1827/

Sorry to ask newbie questions but I really want to understand this. I built a ball valve cannon and was thoroughly impressed but after awhile it got tedious opening the valve and it also resulted in inconsistent shots.

Yes...It's been done many times before.

Just take out the solenoid and fill in the pilot hole with epoxy for pneumatic modification.
Although you can go without modifying it, it would have a much larger increase in opening time if you did.
Sprinkler valves have a diaphragm inside them which closes onto a port that leads to an air chamber, there is a small hole in the diaphragm which equalises the pressure on both sides of it. When the volume of air (pilot volume) is exhausted from above the diaphragm, the diaphragm quickly parts from the chamber port to allow the compressed gas to enter the barrel port from the air chamber.