Water TowerTechnical Concepts
Water tanks help maintain volume and pressure for the distribution of potable (safe to drink) water through pipes to homes, business and other users. The type of tank selected is mostly dependent on the storage capacity, site elevation, cost and appearance.
- Volume: At the end of the water treatment process, a large volume of water is stored in tanks for use when needed. Water tanks are typically filled during periods of low usage and drained during times of heavy use, ensuring that there is always water available when people need it.
- Pressure: For clean water to reach customers it must have sufficient pressure. There are two ways to ensure sufficient pressure is provided to distribute water from a tank:(a) Build the tank on a high elevation or (b)Build the tank in such a way that the water is stored high enough in the air.
Typical Tank Parts
Vent: For closed top tanks,venting must be provided to safeguard against excess pressure or vacuum buildup when the tank is being emptied or filled.
Hatch/ Manway: Allows access into the tank.
Ladder: Allows worker to reach the roof of the tank for repairs or maintenance.
Overflow:Allows excess water to be drained from the tank in case of over filling to reduce damage to tank.
Column (Elevated only): Used to support the weight of the water in the tank.
Riser (Elevated only): Where water is pumped into the tank as well as where water is drained from the tank for potable water use.
Strut/ Rod (Elevated only): Used to stabilize the tank and keep columns from buckling.
Potable (safe to drink) water tanks come in two main types; ground storage and elevated tanks.
- Ground Storage Tanks:As shown in Figure 2, these are cylindrical flat-bottom tanks which are directly supported by the ground. When the height of the ground storage tank is less than or equal to its diameter, it’s called a reservoir and when the tank height is more than its diameter it’s called a standpipe. This style of tank can hold as much as 10,000,000 gallons of water. The USGS Water Science School estimates each person uses 80-100 gallons of water per day.Large ground storage tanks provide the most storage.
Figure 2 - Ground Storage Tank
Elevated Tanks (Water Towers):These consist of water tanks raised in the air with supporting structures below. Since water pressure increases with height, they are typically used to ensure that sufficient water pressure is provided for distribution using the forces of gravity. As shown below, elevated tanks consist of several different types.