When blowing down the water column, what should the water do?

When blowing down the water column, the primary purpose is to ensure that the gauge glass accurately reflects the water level in the boiler. During this process, the water in the gauge glass should refill quickly to provide a clear and indicative reading. The action of blowing down removes sediment and other impurities that may have accumulated, thereby helping to maintain the accuracy of the water level indication.

It's essential for operators to have a reliable gauge glass reading to prevent situations like low water conditions, which can lead to dangerous boiler operations. The quick refilling of the gauge glass confirms that the water column is intact and functioning correctly, allowing the operator to monitor the boiler's water level accurately.

The other options are not appropriate actions during this process. Evaporation would not be expected during blowing down; draining completely would render the gauge glass ineffective; and turning off the burner is not needed unless there is an imminent safety issue unrelated to the blowing down procedure.