Some personal expereince with solenoid valves ...
Orbit Watermaster 1"
Model 57461 (Jar-Top) = this valve is poor for air cannons because the valve itself leaks. Air tends to exit the valve immediately as soon as it is pumped. Quick pumping allows you to eventually seal the diaphragm but it will lose pressure rapidly afterwards.
Price ~12 USD + tax (Sept 2006)
Model 57101 = this valve, like its 3/4" counterpart, has been the preferred valve due to absence of a guide rod. The bleed lever is also more convenient. The older stock usually works well. But recently manufactured ones seems to have defects in the diaphragm. 3 out of 5 I've recently purchased have been defective. Opening the valve revealed that the white plastic portion around the neoprene is of poor quality. There are fragments of the white plastic around the seal-facing ring and the ring itself is not even. Attempts to scratch the white portion clean allow the valve to eventually hold pressure but it loses it as quickly as the Jar Top. Same symptoms as if PVC fragments were lodged in diaphragm. This appears to be true with those with stamps of 5XXXXX (six digits). It could be a recent quality control issue. The two that worked only had a 5 digit stamp. Hopefully this issue is resolved soon.
Price ~13 USD + tax (Sept 2006)
Model 57020 = old manufacture, seen rarely
Rainbird
Model CP100 = Slightly bigger than the Orbit and more expensive. The diaphragm does not seal as quickly as well functioning Watermasters. But it will seal eventually. The trick is to pump it rapidly for the valve to equalize. At 20psi the valve should hold pressure consistently. The bleed screw is directly in the center of the diaphragm.
Price ~16USD+tax (Sept 2006)
