What type of valve is commonly used for main control valves in sprinkler systems?

The post-indicator valve (PIV) is commonly used for main control valves in sprinkler systems because it provides a clear visual indication of whether the valve is open or closed, which is critical for emergency operation and maintenance. The PIV is typically installed in a visible location, making it easier for firefighters and maintenance personnel to assess the valve's status quickly during emergencies. It is designed to withstand high pressures and is specifically constructed for use in fire protection systems, ensuring reliability when needed most.

While other types of valves such as gate valves and butterfly valves may be used in various applications, they do not provide the same level of visibility regarding valve status as a PIV. A gate valve is often used for shut-off purposes but lacks the indicator feature. Relief valves serve a different function, primarily for pressure relief in systems rather than main control, and are not suited for use as primary shut-off valves in sprinkler systems. Therefore, the post-indicator valve is the preferred choice in this context.