In the 1800s, New York City required that all buildings higher than six stories be equipped with a rooftop water tower. This was necessary to prevent the need for excessively high pressures at lower elevations, which could burst pipes.
When high-rise residents turn on their taps to have a drink of water, take a shower or wash the dishes, the water comes from a tank located on the roof of the building. In addition to serving as a storage device, the tank creates water pressure through gravity which brings water to each apartment as needed.
The original water tower builders were barrel makers who expanded their craft to meet a modern need as buildings in the city grew taller in height. Even today, no sealant is used to hold the water in. The wooden walls of the Water Tower are held together with cables but leak through the gaps when first filled. As the water saturates the wood it swells, the gaps close and become impermeable.
The rooftop water towers store 25,000 litres to 50,000 litres of water until it is needed in the building below. The upper portion of water is skimmed off the top for everyday use while the water in the bottom of the tower is held in reserve to fight fire. When the water drops below a certain level, a pressure switch, level switch or float valve will activate a pump or open a public water line to refill the water tower. (wikipedia)
You will be able to tell I really fell in love with those tanks...
