thought about this in the am. keeping in mind that irrigation systems have 40-60psi at the entry end of the valve all the time, perhaps the spring is there to keep the system shut until the valve is energized and then it opens. in our system, the valve wouldn't open due to the low water pressure with the pump off, but as soon as you start filling, pressure is there, and no spring to keep it shut? since the valves in a typical irrigation system do not have power constantly, only when opened, something must be there to counteract the force of the water pressure at the entry.

thoughts on that?