My static pressure is 78 psi and Im going to be using Rainbird 5004's with the internal pressure regulator. Do I need to use a pressure regulator for the entire system? And if a regulator is used does that have an effect on the GPM?
Static pressure is not operating pressure. Including pipe and fittings and valves and backflow preventer, you could lose 20 psi, and that's before you turn on a zone.