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

The function of a master valve in an irrigation system primarily serves to shut off water to the entire system when irrigation is not in operation. This feature is crucial for preventing water waste and ensuring that the system does not leak or overwater the landscape when it is not actively irrigating.

A master valve is typically installed upstream of the zone valves and acts as a safeguard. When the irrigation controller signals that the irrigation cycle is complete, the master valve closes and stops the flow of water to all zones, which helps conserve water and reduce water bills.

While there are other components in the irrigation system that can regulate water pressure, monitor soil moisture, or control flow rates, the specific role of the master valve is to provide an efficient means of stopping the water flow when irrigation is not needed, making option B the correct answer.