Which device is used to stop water flow at a zone or circuit level within a valve box?

• A. Mainline isolation valve
• B. Control valve
• C. Drain valve
• D. Unions

Answer: (B)

The device used to stop water flow at a zone or circuit level inside a valve box is the control valve. In irrigation, each zone typically has its own control valve housed in a valve box. This valve is opened or closed by the irrigation controller to supply or cut off water to that specific zone, allowing independent control of multiple zones without affecting the rest of the system. A mainline isolation valve shuts off water to a larger portion of the system, not just a single zone. A drain valve is intended to vent or drain water from the line for relief or winterization, not to regulate normal flow to a zone. Unions are fittings that join pipes and don’t control flow.