What position must all main water control valves be kept in?

The correct answer is that all main water control valves must be chained and locked in the open position. This practice is essential for ensuring that the water supply remains available for fire suppression systems when needed. By keeping the valves in an open position and secured with chains and locks, it prevents unauthorized access or accidental closure, which could compromise the effectiveness of the standpipe or sprinkler system during an emergency.

In fire protection systems, maintaining access to water is crucial for the system's functionality. The chaining and locking mechanism serves as a safety measure to uphold compliance with codes and standards, ensuring that the systems are always ready to operate when required.

This helps in maintaining a clear protocol for the operational state of these critical components, supporting overall safety and emergency preparedness within a building.