They stand at the crest of the New York skyline like strange, steampunk sentinels. Their design has changed little in more than a century, and though they resemble a relic from a forgotten time, wooden water tanks remain a fixture of the cityscape [1]. Besides, they are an essential part of the city's water delivery system, which feeds water use facilities and fire protection vessels in 90 percent of structures over six stories high.

New York water containers have been a presence on the city's skyline since the mid 19th century. Officials estimate that there are between 10,000 and 15,000 wooden tanks in the city's five boroughs.

According to Wikipedia, in the 1800s, New York City required that all buildings higher than 6 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.

How it works? According to Bryan McShane, "water is pumped to the tanks and then gravity fed into buildings to maintain water pressure for drinking fountains, bathrooms and kitchens, and standpipes, conduits that carry water for fighting fires. When water gets too low, a tank operates much like a standard toilet. A float valve in the tank sends a signal to the pump in the basement of the building to lift water into the tank until it is filled".

The rooftop tanks store 5,000 to 10,000 gallons 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 tank is held in reserve to fight fire. Fire insurance rates are normally lower in a community in which the water system has water towers.

In modern times, the towers have become fashionable in some circles. As of 2006, the neighborhood of Tribeca requires water towers on all buildings, whether or not they are being used.

As you will see in the videos, two companies in New York build water towers, both of which are family businesses in operation since the 1800s. Even though there are steel constructed tanks, wooden ones are preferred because they can be easily assembled and transported to rooftops in parts and cost less.

More info and sources: 1, 2, 3, 4, 5