Question
I have a commercial system. System is pressurized at all times. The system is about 20 years old and mainline breaks are becoming a common occurrence. There are 2 old Rainbird RC1260 controllers on the property. (controllers are side by side) I want to put a master valve (200 PGA valve) just downstream of the pressure switch. This way when controller(s) turns on the system it is then pressurized.  Now here is the question: How can I use 2 controllers on 1 master valve. I know I would need a relay(s), but what type and how would I go about wiring up the relay(s). I proposed removing the 2 controllers and installing 1 newer controller, but they are on a budget and want to keep the 2 controllers.
Oh yeah, the controllers do not run simultaneously. They run at different times.
Thanks a lot for your help.

Answer
Master valve is a GREAT idea. I don't think you will need a relay switch.The important thing is that the transformers for the 2 controllers are in-phase together. Are they plugged into the wall or hard-wired? If I remember the RC controller has the transformer in the cabinet and a white, a black, and a green wire coming-out from below it... Basically make sure that black, white, and green are connected the same or in the same sequence/order all the way back to the electrical panel. This is hard to describe as a picture would be easier... also check with a volt meter that when one common is sending power the other is not. one more location to make the wire switch if you need to is after the transformer.

Is this making sense?