NC EOG Practice Test 13

How a Water Tower Works

¹In many towns, the tallest thing around is not a building. It is a big tank on tall legs, often painted with the town's name. Water towers are so common that most people barely notice them. But these towers do an important job: they help make sure that when you turn on a faucet, water comes rushing out.

²A town's water usually starts in a river, a lake, or a well. It is cleaned at a treatment plant, where dirt is filtered out and germs are killed. Then powerful pumps push it through large underground pipes called water mains. Some of the water travels up a pipe inside the tower and into the tank at the top, where it waits until it is needed.

³Here is the key idea: water is heavy, and gravity is always pulling it down. When water is stored high above the ground, its weight presses down on the water in the pipes below. The higher the water sits, the greater the water pressure in the pipes. That is why towers are built taller than the homes and buildings they serve. Without enough height, the water would not have enough pressure to rise to an upstairs sink.

⁴Why not just use pumps all the time? Pumps could do the job, but people do not use the same amount of water all day. In the early morning, when families are showering and making breakfast, a town uses a lot of water. In the middle of the night, it uses very little. To keep up with the morning rush using pumps alone, a town would need pumps big enough for its busiest moment, and most of the day they would run far below their capacity. A water tower solves this problem. The pumps work at a steady pace and fill the tank when people are using less water, often at night. During busy hours, the tower supplies the extra water, and the level in the tank drops.

⁵Water towers are also a backup. If the power goes out, the pumps stop, but gravity does not. The stored water can keep flowing to homes for a while. Firefighters count on this, too, because putting out a large fire can take a huge amount of water very quickly.

⁶Many towers hold enough water to supply their area for about a day. So the next time you pass a water tower, remember that it is not just a giant can on stilts. It is a simple, clever machine that runs mostly on gravity. Towers come in many shapes, too. Some look like giant golf balls sitting on tees, and a few towns have painted theirs to look like peaches or other local favorites.