Water tower

A water tower, watershed, or elevated water tower is a large elevated water storage container. The term "tower" speaks to its elevation and is constructed for the purpose of holding a supply of water at a height sufficient to pressurize a water supply distribution system. Pressurization occurs through the elevation of water; for every 2.31 feet of elevation 1 PSI (pounds of pressure per square inch) is produced. 100 feet of elevation (@2.34=1PSI) produces 43.3 PSI of pressure, which is enough pressure to operate and provide for most domestic water pressure and distribution system requirements.

Many water towers were constructed during the Industrial Revolution; some are now considered architectural landmarks and monuments, and may not be demolished. Some are converted to apartments or exclusive penthouses.

In certain areas, such as New York City, smaller water towers are constructed for individual buildings.

Construction

A variety of materials are used to construct the typical water tower; steel and reinforced or prestressed concrete are the most often utilized, with wood, fiberglass, and brick also in use today. The tower is usually spherical, cylindrical, or an ellipsoid, and has a minimum height of approximately 20 feet and a minimum of (12 ft) in diameter. A standard water tower typically has a height of approximately 120 feet (40 m). Most water towers have an interior coating to protect the water from the effects of the containment material.

Purpose

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;

* Water towers are able to supply water even during power outages, because they rely on pressure produced by elevation of water (due to gravity) to push the water pipes into domestic and industrial water distribution systems; however, they cannot supply water for a long time without electricity, because a pump is required to refill the tower.

* A further purpose is that a water tower serves as a reservoir to help with water needs during peak usage times. The water level in the tower typically falls during the peak usage hours of the day, and then a pump fills it back up during the night. This process also keeps the water from freezing in cold weather, since the tower is constantly being drained and refilled.

Operation

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thumb|left|400px|How Roihuvuori water tower works:">
1. Pump station
2. Reservoir
3. Water userThe 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 be sized to meet peak demands. During periods of low demand, jockey pumps are used to meet these lower water flow requirements. The water tower reduces the need for electrical consumption of cycling pumps and thus the need for an expensive pump control system, as this system would have to be sized sufficiently to give the same pressure at high flow rates.

Very high volumes and flow rates are needed when fighting fires. With a water tower present, pumps can be sized for average demand, not peak demand; the water tower can provide water pressure during the day and pumps will refill the water tower when demands are lower.

Decoration

Water towers can be surrounded by ornate coverings including fancy brickwork, a large ivy-covered trellis or they can be simply painted. Some city water towers have 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 Granger, Iowa has two water towers, labeled HOT and COLD. "The House in the Clouds" in Thorpeness was built to resemble a house in order to disguise the eyesore, whilst the lower floors were used for accommodation. When the town was connected to the mains water supply, the water tower was dismantled and converted to additional living space.

Sapp Bros. truck stops use a water tower with a handle and spout – looking like a coffee pot – as the company logo. Many of their facilities have decorated actual water towers (presumably non-functional) on-site.

The first and original "Mushroom" – Svampen in Swedish – was built in Örebro in Sweden in the early 1950s and later copies were built around the world including Saudi-Arabia and Kuwait.Fact|date=September 2007

Many small towns in the United States use their water towers to advertise local tourism, their local high school sports teams, or other locally notable factoids (see images below).

Uses today

Water towers are very common in India, where the electricity supply is erratic in most places.

In many countries, water towers have been taken out of the water supply system and replaced by pumps alone. Water towers are often regarded to be monuments of civil engineering.Fact|date=August 2008 Some are rejuvenated and converted to serve modern purposes. For example, the Wieża Ciśnień in Wroclaw, Poland.

Historically, railroads that made use of the steam locomotive required a means of replenishing the locomotive's water reservoirs. Water towers were common along the railroad. Filling these reservoirs was most commonly achieved by means of a water tower feeding one or more water cranes, usually located at stations and locomotive sheds.

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 cellular telephone service.

New York City

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.Fact|date=September 2008 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. Two companies in New York build water towers, both of which are family businesses in operation since the 1800s. ["Wondering About Water Towers" by Debbie Elliott. "All Things Considered", 2 Dec 2006. National Public Radio. http://www.npr.org/templates/story/story.php?storyId=6567297 (includes pictures)]

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 walls are held together with cables but leak through every gap when first filled. As the water saturates the wood it swells, the gaps close and become impermeable.cite news|title=Longtime Emblems of City Roofs, Still Going Strong|author=Charles, Jacoba|publisher=The New York Times|date=2007-06-03|url=http://www.nytimes.com/2007/06/03/nyregion/thecity/03wate.html?_r=1&ref=thecity&oref=login]

The rooftop water towers 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 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 actuate a pump or open a public water line, to refill the water tower.

Famous towers

Famous water towers in the United States include:
* Chicago Water Tower
* Volunteer Park Water Tower, Capitol Hill, Seattle, Washington
* Warner Bros. Studios Water Tower, Burbank, California (In the animated TV series "Animaniacs", it was used to incarcerate the characters Yakko, Wakko, and Dot, as well as their home.)
* Peachoid next to I-85 on the edge of Gaffney, South Carolina
* Earful Tower at Disney's Hollywood Studios
* Florence Y'all Water Tower in Florence, Kentucky
* [http://www.worldstallestwatersphere.com/ Union Water Sphere] in Union Township, New Jersey
* Ypsilanti Water Tower- Winner of the Most Phallic Building contest
* [http://en.wikipedia.org/wiki/
] in Rochester, Minnesota

Famous water towers in the UK include:
* Dock Tower in Grimsby
* House in the Clouds in Thorpeness, Suffolk
* Jumbo in Colchester, Essex

Famous water towers in Slovenia include:
* Brežice Water Tower in Brežice

Gallery

See also

*American Water Landmark
*Hyperboloid structure

References

External links

* [http://science.howstuffworks.com/water.htm HowStuffWorks.com on Water Towers]
* [http://www.muuka.com/finnishpumpkin/towers/tower.html Photographs of different kinds of water towers in Finland]
* [http://www.catsupbottle.com/ World's Largest Catsup Bottle Website]
* [http://www.watertowers.de/ International Watertower Archive]
* [http://www.tfh-berlin.de/~rau/wassertuerme.html German Watertower Archive]
* [http://watertank.net/why-we-use-plastic.html Water Storage Considerations Specifically CFR Title 21 Part 129. US Government document]
* [http://www.steel.org/AM/Template.cfm?Section=Pipes_and_Tanks1&TEMPLATE=/CM/HTMLDisplay.cfm&CONTENTID=1634 American Steel and Iron Institute list of water towers]