In the operation of any boiler, even a teakettle, it is essential always to keep enough water in
the boiler. If it should run dry the metal would become red hot, soften, and rupture. At the
same time it should not be filled to a point where there is no room for the steam to collect.
To check the water level, a water gage is fitted to the steam drum. This, at all times shows
the water level in the boiler.