I was afraid of that. I don't think you'll get the sort of short on-off performance you'll need for that sort of application out of normal irrigation valves. They tend to take multiple seconds to turn on and off; the solenoid controls a very small flow of water which changes the pressure on a larger diaphragm, and THAT switched the main flow. I don't know where you'd get the high-speed water valves of the sort you'd need, and I rather suspect that high power draw is going to be part of their nature, since (I think) you'll have to have electrical force completely overcome water force.