Not quite on topic, but...
From:
“The Story of American Railroads”,
by Stewart H. Holbrook,
Crown Publishers, New York,
Copyright 1947.
(Chapter V, The work of the Age.)
“Some of the farmers must have sat up nights figuring how to trim the Erie. One of them, who had a worthless place on a hill near Middletown, heard that the road was looking for good sources of water for the engines. The road ran through this farmer’s place, and at one spot went through a cut where the ground was higher than the locomotive. On a level spot above this site the farmer dug a sizable reservoir, lined it with clay, and by means of small ditches and a little patience, filled the depression with good rain from heaven. Then he called on President Loder of the Erie, who happened to be in Middletown. He told Loder that he, the farmer, was a most fortunate man indeed, in that God had put on his fine farm a wonderful pond of never failing water, fed by deep springs; that the pond was handy to the Erie tracks and that for a consideration of $2,500, modest in view of the circumstances, he would sell to the Erie all rights to the pond.
“Loder and Major Brown, the Erie’s chief engineer, went to look, and sure enough there was a pond of water sufficient to fill the tanks of all the locomotives possessed by Erie. They paid the man his $2,500, and set a crew to work laying iron pipe from the pond to a tank built beside the tracks. When the valve was opened, the tank filled up wonderfully fast, but in doing so the pond went stark dry, and dry it remained."
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Back to the question. Some tanks did not have a "valve" other than a flexible coupling (leather hose). When the spout was "up" the water just reached a level point below the raised opening of the spout... water flowed when the spout was lowered... of course that could (and did) freeze in cold weather. Others had the valve deep in the tank where the water itself would insulate it. The tanks seldom froze all the way through, but the part that froze could deplete the amount of liquid water available to fill the tender. In areas where there were sustained freezing temperatures the tanks had heater shacks adjacent to them, but where the weather was milder the tank held enough water that it never froze all the way through.
