Water tower

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For the That '70s Show episode, see "Water Tower (That '70s Show episode)".

Image:Roihuvuori water tower - Helsinki Finland.jpg

A water tower or elevated water tank 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. Many water towers were constructed during the industrial revolution and some of these are now considered architectural landmarks and monuments and may not be demolished. Some are converted to apartments or exclusive penthouses.

1 Construction
2 Purpose of towers
3 Operation of towers
4 Decoration of towers
5 Declining use
6 Further uses
7 Famous towers
8 See also
9 External links

[edit] Construction

Image:NewYorkCityWaterTower.JPG A typical water tower is constructed of steel, reinforced or prestressed concrete or bricks. It is usually spherical or cylindrical and is approximately 50 feet (16 metres) in diameter. It typically has a maximum height of approximately 120 feet.

[edit] Purpose of towers

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:

water may not reach the upper floors of a building;
water may not spray from a tap with sufficient flow
without a water tower, parts of gravity flow water supply systems in hilly areas may be subject to negative pressures (see siphon). Negative pressure in the system may cause shallow groundwater to be sucked into a leaky water supply system, polluting it with microorganisms, dirt, sand, fertilizers, and any other toxic contaminants that may be in the groundwater;

[edit] Operation of towers

Image:Roihuvuori watertower2.png

The height of the tower provides the hydrostatic pressure for the water supply system, and it may be supplemented with a pump. The volume of the reservoir and diameter of the piping provide and sustain flow rate. However, relying on a pump to provide pressure is expensive; to keep up with varying demand, 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 or popular shows; also, high flow rates are needed when fighting fires. With a water tower present, pumps can be sized for average demand, not peak demand; the tower can provide water pressure during the day and the pumps can refill the water tower at night when demand is very low.

[edit] Decoration of towers

Water towers can be surrounded by ornate coverings including fancy brickwork, a large ivy-covered trellis, etc., or it can be simply painted. Some city water towers had the name of the city painted in large letters on the roof, as a navigational aid to aviators. Sometimes the decoration can be humorous, as Pratt, Kansas has two water towers, labeled HOT and COLD.

[edit] Declining use

In many countries water towers are taken out of the water supply system and replaced by pumps only.

Water tower by V.Shukhov - the world's first hyperboloid structure, Russia, 1896	Typical U.S. water tower, Fort Sill, Oklahoma.	The local water tower at Grandview in Hampton, Virginia.	The Victorian water tower on Shooters Hill, London.
Modern U.S. water tower in Carmel, Indiana.	Unique water tower in the shape of a ketchup bottle, Collinsville, Illinois (This is also the world's largest ketchup bottle.)	Modern U.S. water tower in Bellaire, Texas.	The Westfield water tower.

[edit] Further uses

Some water towers are also used as observation towers. There are even water towers with restaurants, such as the Goldbergturm in Sindelfingen, Germany. It is also common to use water towers as the location of transmission mechanisms in the UHF range with small power, for instance for closed rural broadcasting service, portable radio, or celluar telephone service.