Search: how does a water tower work
Why: I always just sort of thought of them as storage containers, but I today I realized that doesn't make any sense.
Answer: In most towns, the water people drink comes from either a well, a river, or a reservoir/local lake. The water is treated in a treatment plant to remove sediment and bacteria. The output from the water treatment plant (A) is clear, germ-free water. A high-lift pump (B) pressurizes the water and sends it to the water system's primary feeder pipes (C). The water tower is attached to the primary feeders quite simply by a tube that passes directly through the ground.
If the pump is producing more water than the water system needs, the excess flows automatically into the tank (D). If the community is demanding more water than the pump can supply (like in the morning when people shower, brush teeth, etc.), then water flows out of the tank to meet the need.
Source: HowStuffWorks
The More You Know: 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.
