A Fire Hydrant is an above-ground connection that provides access to a water supply for the purpose of fighting fires. Fire hydrant systems are an installation of pipes, water tanks, pumps, hydrant outlets and / or hose reels.
Hydrant Systems can be of two types:

(a) External Hydrant System, where the hydrants are installed in the open, like the city or town water mains, or hydrant systems installed in the open areas in industrial or such other occupancies and

(b) Internal Hydrant System, installed in buildings or structures to be protected