Final answer:
The indicating valves in a compactor sprinkler system are required to be visibly open to ensure that water can flow unimpeded in the event of a fire, as part of fire safety regulations.
Step-by-step explanation:
All indicating valves in the compactor sprinkler system shall be visibly open. This requirement is crucial for ensuring that the system is ready to operate in case of a fire and that water can flow freely through the sprinkler heads to suppress the fire. Fire safety regulations often mandate that these valves be locked or sealed in the open position, and they must often be equipped with tamper switches that send an alarm if the valve is closed. These safety measures prevent accidental or intentional closure of the valves, which could severely compromise the effectiveness of the sprinkler system during a fire.
In the context of the compactor sprinkler system, the phrase 'All indicating valves shall be ________ open' means that all the indicating valves should be kept fully open. Indicating valves are used to show whether a specific section of the sprinkler system is open or closed. By keeping them fully open, the system can function properly and effectively.