Indicating valves in a compactor sprinkler system must be:

In a compactor sprinkler system, indicating valves play a critical role in ensuring that water flow can be monitored and controlled effectively. The requirement for these valves to be sealed open means that they cannot be accidentally closed or tampered with during normal operations.

When indicating valves are sealed open, it allows for continuous water flow, which is essential for the sprinkler system to function properly in the event of a fire. This provision ensures that the system is always prepared to engage automatically once the fire detection system is activated. Sealing the valve also provides a clear indication that the valve is in an open state for maintenance personnel and first responders, which enhances safety and efficiency during emergency situations.

This aspect of sealing reinforces accountability and reliability in the system's operation, ensuring that the sprinklers can perform their lifesaving function without interruption. In contrast, other configurations like manual operation or remote operation would introduce unnecessary complexity and potential failure points.