Why don't fire hydrants freeze and crack in the winter time?

Question

Why don't fire hydrants freeze and crack in the winter time?

Answer 1

You have two good answers above that describe the typical "wet" hydrant, the kind used in cities and larger towns. There is also the self-explanatory "dry" hydrant that will be found in rural areas.

Answer 2

There is no water in the fire hydrant until the top valve is opened.

Answer 3

Because they're made out of materials to prevent that from happening. ;)

Answer 4

Good question, my guess would be that the majority of the water is underground, which is generally above freezing.

Answer 5

The valve is not at the top but rather down at the water pipe underground.  So the nut on the top to turn on/off the water is the same as the valve on some outside water taps for houses in that it is long and controls open and closed from a distance so the freezing problem is reduced.  Some that were used recently may suffer from freezing as water may still be in the hydrants upper area.

So you have the nut to open and close the valve at the top of the hydrant but the valve is down a few feet below ground so as to stop the freezing problem.  The water pipes supply the houses/businesses so water is almost always flowing in the pipes.

Answer 6

As the previous posts state, the water is not in the hydrant except when the valve is opened. The nut on top of the  hydrant is attached to a long stem which opens the valve several feet below ground and allows water to flow up to the hydrant and out the fittings. When the valve is closed, the water in the hydrant drains out through a set of 'weep holes' down at the valve.

ps - when you see a car in the movies hit a fire hydrant and the water comes gushing up - that is just in the movies, it doesn't happen in the real world unless the valve somehow gets torn off, which is very unlikely.