After some trial and error, I found that to stop the air from coming out the top, I had to let the pressure build up in the tank to about 50psi or more, then attached the hose. This quick pressure increase caused the valve to close as it would if water was flowing through. I then cycled through the zones. The heads didn't stick straight up but there was enough pressure to blow out the water. Once I connected the hose, the pressure never got much over 25psi, which was barely enought. I don't know...
David, did you get an answer to your original question? I have the same valve. I also need to understand how to stop the air from coming through the backflow plunger.
