Why do fire hydrants not freeze and burst in the winter? The water is theoretically above the freezing line, no?
In: Engineering
There are two types of pressurized fire hydrants. Wet barrel and dry barrel. Wet barrel hydrants are found in warm climates only and the shut-off valve is on the hydrant itself. These hydrants are always full of water, or wet. Dry barrel hydrants are found in climates with freezing temperatures and the shut-off valve is located many feet below ground (below the frost line), but still controlled on the hydrant by a large rod internally that goes into the ground. These hydrants are only full of water when they’re turned on and they drain when turned off. They don’t freeze when not in use because there is no water in them.
If a wet barrel hydrant was installed in a cold climate, it absolutely would freeze! Wet barrel hydrants are also the ones that turn into fountains in the movies when hit by a car.
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