The problem with a steam driven pumper was they had to raise steam to move at all.
Some steam driven pumpers may have been kept 'hot' with steam pressure in the boiler while slumbering in the fire house. That was also true in the case of some horse-pulled steam pumpers.
For instance, linked is an instruction manual for horse pumpers, "Handbook For American Fire Engine Company Steam Engines" that references connecting the pumper to "house steam" while in the fire house:
https://www.legeros.com/history/steamers/1897-manual.shtmlOne section from that Pumper Handbook booklet ...
THE ENGINE HEATER.
A stationary heater for the fire engine consists of a small boiler, placed at some convenient point near the same when in quarters. It is connected with the engine boiler by means of automatic couplings and suitable circulating pipes, the entire arrangement being adapted to maintain the water contained therein at any temperature desired.
Although the best types of fire engines boilers require but a few minutes time to generate a working pressure from cold water, the general adoption of the many modern improvements for facilitating the movements of the men and apparatus has made the stationary heater an essential part of a complete equipment.
A very reliable and satisfactory heater for this duty is built by the American Fire Engine Company. It is fully shown in the accompanying illustrations, and explicit directions for operating the same are appended.
Experience proves that the life of the boiler is prolonged by being kept constantly in a state of activity, and the elevated temperature of the water insures prompt and efficient work by the steamer at the very time when a few moments delay may breed disaster.
It seems reasonable to expect that the same "house steam" system already in the fire house would have been used to keep steam propelled pumpers ready to move in short order (after disconnecting the "house steam" lines, of course).
