Which indicator shows that a PIV is closed?

The correct choice, which indicates that a Post Indicator Valve (PIV) is closed, is that the visual indicator reads "shut." This is important because PIVs are designed to show the status of the valve with a clear and easily interpretable visual indicator. When the valve is closed, it ensures that the water supply to the main fire service line is shut off, which is critical information for firefighters responding to an incident. Understanding this indicator allows firefighters to assess the availability of water for firefighting operations efficiently.

Other indicators might suggest a change in the valve's status but don’t provide the explicit information that a reading of "shut" offers. For instance, while a square flag might be used in some systems as a visual cue, it is not universal and may not clearly indicate the closed status in all situations. The gurgling sound and stopping of a spinning target could imply that the valve is closed, but these are not definitive indicators of the valve status according to standard practices. Thus, the most reliable and standardized indicator that communicates the closure of the PIV is when the visual indicator reads "shut."