Alto, California .
Why Are Water Towers Built So High?
We have passed through small towns and cities where the water tower is by far the highest structure in sight. The name of the city is often emblazoned around the surface of the mighty edifice.
But why are the water towers necessary anyway when most communities have reservoirs? And why are they so tall?
We got our answer from Dr. Paul J. Godfrey, director of the Water Resources Center at the University of Massachusetts at Amherst:
The task of providing water through a municipal distribution system requires both sufficient volume to meet normal consumption, emergency consumption (such as for fighting major fires), and sufficient pressure to operate household and industrial devices.
The water tower provides, by its volume, a reservoir that can meet short-term needs during periods of high water use, usually in the morning and around dinner time, and allows the various sources of supply, reservoirs, or wells, to catch up during lower demand. The volume chosen for a facility usually assumes that a sufficient volume must be available to meet simultaneous demand during the high consumption period and a major fire. All of these functions do not require a particular water height.
But water pressure is provided by the height of the tower. Water seeks its own level. For example, if we fill a water hose with water and hold each end of the hose at exactly the same level, no water flows out. But if one end of the hose is raised, water flows out of the other end…. The more water, and hence weight, above the lower end, the greater the force of water flowing out of the hose. The role of the water tower is to provide an elevated weight of water sufficient to provide adequate pressure at all outlets in the system.
The alternative would be to install electrical pumps to force water out of other reservoirs, but this is an inefficient technology. As peter Black, president of the American Water Resources, told Imponderables , with a pump system “You would have to activate the pump every time anybody wanted any water.”
The water tower may be lower tech than an electrical pump, but with the precautions outlined by Dr. Godfrey, it does the job well over any terrain:
To create adequate pressure for all parts of a municipality, the water tower must be higher than all the municipality’s water taps, sufficiently high to create fire-fighting pressure at all hydrants. In some cities, the municipal supply does not provide enough pressure for tall buildings, so booster pumps and another storage tank on top of the building supplements pressure. [In New York and other big cities, standpipes are placed in front of tall buildings to insure that water can be delivered to the top of the building.]
Water pressure in all areas of the municipality must be carefully controlled. Low pressure will be dangerous in a serious fire and will produce complaints from those who like brisk showers. High pressure will wear out valves and gaskets faster and cause excessive system leakage. Towns with high hills will often have squat water tanks on the highest hill and install pressure regulators to reduce pressure in the valleys. Towns with no hills must compensate by building an artificial hill, the water tower, which is higher than the tallest building.
So those water towers aren’t so high just to serve as a monument to the ego of the mayor. The tall water tower ends up saving energy and money. But as Jay H. Lehr, executive director of the Association of Ground Water, explains, even our hero, the water tower, isn’t perfect: “Of course, there is no free lunch, as electrical energy is used in pumping the water into the storage tower in the first place.”
Submitted by Cheri Klimes of Cedar Rapids, Iowa. Thanks also to George Armbruster of Greenbelt, Maryland; Gary Moore of Denton, Texas; and Jason and Bobby Nystrom of
Why Are Water Towers Built So High?
We have passed through small towns and cities where the water tower is by far the highest structure in sight. The name of the city is often emblazoned around the surface of the mighty edifice.
But why are the water towers necessary anyway when most communities have reservoirs? And why are they so tall?
We got our answer from Dr. Paul J. Godfrey, director of the Water Resources Center at the University of Massachusetts at Amherst:
The task of providing water through a municipal distribution system requires both sufficient volume to meet normal consumption, emergency consumption (such as for fighting major fires), and sufficient pressure to operate household and industrial devices.
The water tower provides, by its volume, a reservoir that can meet short-term needs during periods of high water use, usually in the morning and around dinner time, and allows the various sources of supply, reservoirs, or wells, to catch up during lower demand. The volume chosen for a facility usually assumes that a sufficient volume must be available to meet simultaneous demand during the high consumption period and a major fire. All of these functions do not require a particular water height.
But water pressure is provided by the height of the tower. Water seeks its own level. For example, if we fill a water hose with water and hold each end of the hose at exactly the same level, no water flows out. But if one end of the hose is raised, water flows out of the other end…. The more water, and hence weight, above the lower end, the greater the force of water flowing out of the hose. The role of the water tower is to provide an elevated weight of water sufficient to provide adequate pressure at all outlets in the system.
The alternative would be to install electrical pumps to force water out of other reservoirs, but this is an inefficient technology. As peter Black, president of the American Water Resources, told Imponderables , with a pump system “You would have to activate the pump every time anybody wanted any water.”
The water tower may be lower tech than an electrical pump, but with the precautions outlined by Dr. Godfrey, it does the job well over any terrain:
To create adequate pressure for all parts of a municipality, the water tower must be higher than all the municipality’s water taps, sufficiently high to create fire-fighting pressure at all hydrants. In some cities, the municipal supply does not provide enough pressure for tall buildings, so booster pumps and another storage tank on top of the building supplements pressure. [In New York and other big cities, standpipes are placed in front of tall buildings to insure that water can be delivered to the top of the building.]
Water pressure in all areas of the municipality must be carefully controlled. Low pressure will be dangerous in a serious fire and will produce complaints from those who like brisk showers. High pressure will wear out valves and gaskets faster and cause excessive system leakage. Towns with high hills will often have squat water tanks on the highest hill and install pressure regulators to reduce pressure in the valleys. Towns with no hills must compensate by building an artificial hill, the water tower, which is higher than the tallest building.
So those water towers aren’t so high just to serve as a monument to the ego of the mayor. The tall water tower ends up saving energy and money. But as Jay H. Lehr, executive director of the Association of Ground Water, explains, even our hero, the water tower, isn’t perfect: “Of course, there is no free lunch, as electrical energy is used in pumping the water into the storage tower in the first place.”
Submitted by Cheri Klimes of Cedar Rapids, Iowa. Thanks also to George Armbruster of Greenbelt, Maryland; Gary Moore of Denton, Texas; and Jason and Bobby Nystrom of
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