What is the purpose of the master control valve besides it shutting down the entire sprinkler system? I've read in a book its not needed but a great insurance for conserving water. I just confused because it mentioned was an automatic valve, at first, then a gate valve later (but not the main shutoff). Does it have a place to be wired in a controller (Hunter Pro-C)? Does open each time a zone valve is open? What happens if a zone valve opens and the main control doesn't? i'm at the point in my installation where I have installed most of the PVC pipes underground, wired up 3 zones in a valve box (front); teed off PVC to the backyard. I'm about to wire up the backyard (3 zones), hook up the RPZ and connect that to the front valves, I'm wondering if I need to -or- should connect 1 more valve right after the RPZ to be the main control valve? Any suggestions?!?