Water tower

A water tower or elevated water tower is a large elevated drinking water storage container constructed to hold a water supply at a height sufficient to pressurize a water distribution system.

Pressurization occurs through the hydrostatic pressure of the elevation of water; for every 10.20 centimetres (4.016 in) of elevation, it produces 1 kilopascal (0.145 psi) of pressure. 30 m (98.43 ft) of elevation produces roughly 300 kPa (43.511 psi), 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 in the United States, smaller water towers are constructed for individual buildings.

The largest man made water tower is located in McBee, South Carolina and holds 1,200,000 US gal (4,500,000 l) of water. This water tower was built and is operated by Alligator Water and Sewer.

1 Construction
2 Purpose
3 Operation
4 Decoration
5 Water Towers around the World
6 Alternatives
7 Famous Towers
8 Gallery
9 See also
10 References
11 External links

Construction

A variety of materials can be used to construct a typical water tower; steel and reinforced or prestressed concrete are most often utilized (with wood, fiberglass, or brick also in use), incorporating an interior coating to protect the water from any effects from the lining material. The reservoir in the tower may be spherical, cylindrical, or an ellipsoid, with a minimum height of approximately 6 metres (20 ft) and a minimum of 4 m (13 ft) in diameter. A standard water tower typically has a height of approximately 40 m (130 ft).

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 pulled 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 hydrostatic pressure produced by elevation of water (due to gravity) to push the water into domestic and industrial water distribution systems; however, they cannot supply the water for a long time without electricity, because a pump is required to refill the tower. A water tower also 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

The height of the tower provides the 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.

Using wireless sensor networks to monitor water levels inside the tower allows municipalities to automatically monitor and control pumps without installing and maintaining expensive data cables.^[1]

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 and motorists. Sometimes the decoration can be humorous, as Granger, Iowa has two water towers, labeled HOT and COLD. The House in the Clouds in Thorpeness, located in the English county of Suffolk, 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.

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 facts. Since the water tower is sometimes the highest point in the town, antennae, public address systems, cameras and tornado warning sirens are sometimes placed on them as well.

Water Towers around the World

Water towers are ubiquitous in the New York City skyline, United States.

In the 19th century, 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. In modern times, the towers have become fashionable in some circles. As of 2006^[update], 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 19th century.^[2]

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.^[3]

The rooftop water towers store 25,000 litres (5,500 imp gal) to 50,000 litres (11,000 imp gal) 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.^[3]

Architects and builders have taken varied approaches to incorporating water towers into the design of their buildings. On many large commercial buildings, water towers are completely hidden behind an extension of the facade of the building. For cosmetic reasons, apartment buildings often enclose their tanks in rooftop structures, either simple unadorned rooftop boxes, or ornately decorated structures intended to enhance the visual appeal of the building. Many buildings, however, leave their water towers in plain view atop utilitarian framework structures.

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. However, this approach is dependent on continuous pumping; if the pumps fail (such as during a power outage), then water pressure will be lost, causing potential public health concerns. Many states require a "boil water" notice to be issued if water pressure drops below 20 psi.

Water towers are often regarded as monuments of civil engineering. Some are converted to serve modern purposes, as for example, the Wieża Ciśnień in Wrocław, Poland which is today a restaurant complex. Others have been converted to residential use.^[4]

Historically, railroads that used steam locomotives required a means of replenishing the locomotive's tenders. Water towers were common along the railroad. The tenders were usually replenished by water cranes, which were fed by a water tower.

Some water towers are also used as observation towers, and some restaurants, such as the Goldbergturm in Sindelfingen, Germany, or the second of the three Kuwait Towers, in the City-State of Kuwait. 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. In hilly regions, local topography can be substituted for structures to elevate the tanks. These tanks are often nothing more than concrete cisterns terraced into the sides of local hills or mountains, but function identically to the traditional water tower. The tops of these tanks can be landscaped or used as park space, if desired.

Alternatives

Alternatives to water towers are simple pumps mounted on top of the water pipes to increase the water pressure.^[5] This new approach is more straightforward, but also more subject to potential public health risks; if the pumps fail, then loss of water pressure will result in potential public health impacts, typically associated with entry of contaminants into the water system. Most large water utilities do not use this approach, given the potential risks.