What is the purpose of a master valve in an irrigation system?

• A. To stop water flow to all zones when the system is not running, preventing leaks and waste.
• B. To regulate flow within each zone.
• C. To bypass the controller in case of power failure.
• D. To provide backflow protection.

Answer: (A)

The main idea is that the master valve acts as the system-wide shutoff on the irrigation mainline. Its job is to stop water flow to all zones when the system isn’t running, which helps prevent leaks and wasted water in case a valve sticks open, a line develops a leak, or a controller isn’t actively turning zones on and off. This is different from regulating flow within a single zone—zone valves and flow-control devices handle that. It’s also not meant to bypass the controller during a power outage, and backflow protection is provided by a backflow preventer, not the master valve.