What should a valve located between the boiler and water column be?

A valve located between the boiler and the water column should be locked or sealed open to ensure that it remains in the open position at all times during operation. This configuration is crucial for maintaining proper communication between the boiler and the water column, which is essential for accurate water level measurement and boiler safety.

If the valve were to be closed or manually operated, it could lead to situations where the water level is not adequately monitored, potentially resulting in unsafe boiler conditions such as low water level, which could cause overheating or damage to the boiler. An automatically operated valve would not provide the same level of reliability and oversight required in a steam boiler system. Therefore, the correct answer emphasizes the importance of ensuring continuous flow and safety within the system, which is achieved by keeping the valve locked or sealed in the open position.