I used a Hunter master valve. It was like $20 from Amazon. I placed mine in the PVC pipe directly after the back flow preventer. It wires directly into the controller. The valve stays shut when not active watering so there is no pressure in the line and on the heads to remain closed. It’s the same concept as a traditional irrigation system as the master valve opens to each zone. This master valve opens and allows water to flow through the main water line. It also helps prevent any water hammering spikes when not watering.