[GeeTwo]

Air is MUCH more compressible than water. This means that compressing a volume of air to 120 PSI takes several thousand times more work than compressing the same volume of water to the same pressure. As a consequence, there is MUCH MUCH MUCH more energy to be released.

In general, only use devices rated for air pressure (not water pressure) to handle air. In particular: DO NOT USE A "SPRINKLER VALVE" to control air pressure. While the pressure/force is no greater, the stored energy in air is three or four orders of magnitude higher than that stored in water at the same pressure. Do not use PVC or other random plastic containers to store air.

For a T-shirt launching air cannon, I recommend at least a 3/4" (and preferably a 1") AIR-rated solenoid, and that all hoses be of similar diameter. With a 3/4" solenoid valve, 3/4" tubing, and 60 PSI pressure, we have thrown t-shirts and foam footballs over our press box onto 9th street; it is unlikely that you will need greater pressure to get t-shirts into the top levels of your stands.