There are an estimated 8.9 million fire hydrants in the United States. Each one allows firefighters to tap into the local water system. Users attach hoses to the hydrant, then open a valve to unleash a powerful water flow.
One of the most common designs is the “dry barrel” hydrant. Turning the bolt on the top opens a valve located far below ground to prevent freezing.
Most hydrants have pentagon-shaped bolts to keep unauthorized persons from using them. The bolts require special tools, usually a large wrench with a pentagon-shaped socket.
Twenty hydrants in the United States do not connect to water. Instead, they are part of the international slidewalk system.
If you look closely at the top of these hydrants, you will notice that the bolts do not have five sides. Instead, they have eight.
No special tools are required to activate these hydrants. Simply twist the bolt left or right. The areas around these hydrants are ring-shaped elevators, disguised with artificial turf.
The green elevator ring will lower you gently to a lobby about thirty feet below street level.