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A water tower is a very large tank constructed for the purpose of holding a supply of water at a height sufficient to pressurize a water supply system.
A typical water tower in the U.S. is constructed of either steel or concrete, is either spherical or cylindrical, is approximately 50 feet (16 meters) in diameter and has a maximum height of approximately 40 feet (13 meters).
The users of the water supply (a town, factory, or just a building) need to have water pressure to maintain the safety of the water supply. If a water supply is not pressurized sufficiently, several things can happen:
- groundwater leaks into the water supply system, polluting it with microorganisms, dirt, sand, fertilizers, and any chemicals that may be in the groundwater;
- the water supply pipe may collapse due to the pressure of the ground above it (normally offset by the water pressure);
- water may not reach the upper floors of a building;
- water may not spray from a faucet with sufficient force or volume.
The mushroom-shaped concrete water tower of Roihuvuori in Helsinki, Finland was built in the 1970s. It is 52 meters high and can hold around 12,000 m³ of water. The head (pressure provided by water depth) provides the water pressure for the water supply system, and it may be supplemented with a pump. However, relying on a pump to provide pressure is expensive; the pump would have to provide a constantly varying output pressure (and thus need an expensive control system), and it would have to be sized sufficiently to give the same pressure at high flow rates. Very high flow rates have been recorded during program breaks during the television broadcast of large sporting events like the Super Bowl.
Water towers can be surrounded by ornate coverings including fancy brickwork, a large ivy-covered trellis, etc., or it can be simply painted. Most city water towers have the name of the city painted in large letters.
Examples of famous water towers include:
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