Drinking Water Storage Tanks (Kids)

A water storage structure such as a water tower or tank, stores water for future use for a community. 

Water storage tanks provide several benefits, including water pressure for the water main pipes in the nearby area, and relief if there is a pressure increase throughout the  nearby water mains. 

Some water towers are tall to provide pressure, while others are placed on top of hills. If the water tank is above ground, they are called elevated tanks. Each foot of height provides .43 PSI (pounds per square inch) of pressure.  A typical house’s water pressure is between 50 and 100 PSI.  The water tower must be tall enough or on a hill tall enough to supply that level of water pressure to all buildings in the area of the tower (called a pressure zone).  Water towers are able to supply water for a period of time even during power outages, because they rely on gravity into pipes.

If a water supply does not have enough pressure, several things can happen:

water tower painted with globe

  • Water may not reach the upper floors of a building;
  • Water may just drip from a faucet;
  • Without a water pressure, negative pressure may occur. Negative pressure in the system may cause shallow groundwater to be pulled into a water pipe, polluting it with dirt, sand, and other groundwater contaminants.



Some water tower tanks are sized to hold about a day’s worth of water for the community served by the tower.  This allows a town to size its pumps for the average rather than the peak demand daily load. The peak daily demand is the amount of water used on the day that had the highest water use.  Sizing the pumps for the average daily load can save communities money in construction and operations.

1. Many water storage tanks are constructed of steel.  The thickness of the steel varies within the tank, depending on the pressure exerted on the tank walls.   The upper walls may be relatively thin, but the lower walls may have a thickness of 2 inches or more.

2. A pipe that runs from the ground to the top of the tank is called a riser.  It brings water into and out of the tank. 

water tanks3. An overflow pipe is necessary on all tanks to safeguard that if water flowing into the tank doesn’t turn off, the water can be safely released out of the tank.  The pipe discharges to a drain below.

4. Air vents allow air to enter and leave the tank as the water level falls and rises.  The water level is measured either by a pressure sensor at the tank base or a level sensor inside.

5. Hatches are installed for entry and ventilation during maintenance and inspection.

6. Multicolumn tanks have a ladder that runs from the ground to the balcony and another that goes up through the access tube to the top of the tank.  This allows maintenance workers to get on top of the tank.

7. Warning or strobe lights on an elevated tank may be required by the Federal Aviation Administration to warn aircraft in the tank’s vicinity, depending on the tank’s height and location.

illustration cutaway view of water tank

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