Water Towers

June 18, 2009 by  


tufail

A big reason for the reliability of an area’s water system is the water tower. You see water towers everywhere, especially if you live in a flat area full of small towns. Each water system has one or more towers. In this article, we will look at how water towers work. The next time you drive by a water tower, you will know exactly what it is doing.

A water tower is an incredibly simple device. Although water towers come in all shapes and sizes, they all do the same thing: A water tower is simply a large, elevated tank of water.

Water towers are tall to provide pressure. Each foot of height provides 0.43 PSI (pounds per square Inch) of pressure. A typical municipal water supply runs at between 50 and 100 PSI (major appliances require at least 20 to 30 PSI). The water tower must be tall enough to supply that level of pressure to all of the houses and businesses in the area of the tower. So water towers are typically located on high ground, and they are tall enough to provide the necessary pressure. In hilly regions, a tower can sometimes be replaced by a simple tank located on the highest hill in the area.

A water tower’s tank is normally quite large. A normal in-ground swimming pool in someone’s backyard might hold something like 20,000 or 30,000 gallons (that’s a lot of water!), and a typical water tower might hold 50 times that amount! Typically, a water tower’s tank is sized to hold about a day’s worth of water for the community served by the tower. If the pumps fail (for example, during a power failure), the water tower holds enough water to keep things flowing for about a day.

One of the big advantages of a water tower is that it lets a municipality size its pumps for average rather than peak demand. That can save a community a lot of money.

Say that the water consumption for a pumping station averages 500 gallons of water per minute (or 720,000 gallons over the course of a day). There will be times during the day when water consumption is much greater than 500 gallons per minute. For example, in the morning, lots of people wake up at about the same time (say 7:00 a.m.) to go to work. They go to the bathroom, take a shower, brush their teeth, etc. Water demand might peak at 2,000 gallons per minute at 7 a.m. — there is a big cost difference between a 500-gallon-per-minute pump and a 2,000-gallon-per-minute pump. Because of the water tower, the municipality can purchase a 500-gallon-per-minute pump and let the water tower handle the peak demand. At night, when demand normally falls to practically zero, the pump can make up the difference and refill the water tower.

In most towns, the water people drink comes from either a well, a river or a reservoir (normally a local lake). The water is treated in a water treatment plant to remove sediment (by filtration and/or settling) and bacteria (typically with ozone, ultraviolet light and chlorine). The output from the water treatment plant is clear, germ-free water. A high-lift pump pressurizes the water and sends it to the water system’s primary feeder pipes.

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