It doesn't prevent all of them. Two or three years ago someone ran over one
here and it looked just like on the movies.
Karl

"B.B." u wrote in message
news
In article ,
jim rozen wrote:

In article , Jeff Wisnia says...

The only thing I can come up with is that there must have been a good
sized air pocket above the valve which got compressed by water pressure
when the valve was opened and closed, 'cause I don't think just water or
the hydrant/riser pipe by itself would store enough to do that.

Hydrants drain down when the valve at the bottom is closed. They're
full of air most of the time - they'de freeze otherwise.

Also prevents a geyser when a car hits 'em. When I was little our
YMCA guy ran over a hydrant on the way from school. I looked down the
hole while we were waiting for the other van to get us and saw the valve
assembly.

--
B.B. --I am not a goat! thegoat4 at airmail dot net
movies.crooksandliars.com/Countdown-Timeline-Katrina.mov