Why doesn the water in fire hydrants freeze during winter?
Dear Straight Dope: Why doesn’t the water in fire hydrants freeze during the winter? It would be quite a problem if firemen showed up to put out a blaze, and no water came out! — Chris Because there isn’t any water in them to begin with. Fire hydrants are equipped with an anti-siphon valve (meaning they are self-draining). The valve seal–the “door,” so to speak–is at the bottom of the hydrant … underground, safely below the frost line, at the point where the hydrant taps into the water main. A long rod runs from this valve to the top of the hydrant. The firefighters put a wrench on the top of the rod to open the hydrant. Once turned off, the water drains from the hydrant back into the ground around it so the barrel from the water main into the hydrant is empty. Hydrants are considered frostproof up to -50 degrees. But the first source of water for firefighters is not the fire hydrant. It’s the fire engine (as opposed to the fire truck, which carries the ladders). A standard fire en
