When travelling through a town or along a highway, you may spot a tall column topped by a huge metal ball. It can look like a futuristic structure or an unusual observation tower, but it is often a water tower: a tank that stores drinking water for nearby households. Its spherical shape is striking, but it is not the only possible solution. It is important to distinguish between why the tank stands high above the ground and why it has a rounded shape.
Spherical and spheroid water towers are elevated water-storage structures. Their height makes it possible to use gravity to create pressure in water pipes, while the tank’s shape is related to its construction, required capacity, available space, and appearance. Not every water tower is a ball, and not every rounded tank is perfectly spherical. Local needs, terrain, cost, and maintenance—not merely eye-catching design—determine which structure is chosen.
What is a tall water tower actually for?
A water tower stores a reserve of treated water and helps balance the difference between how much water is currently pumped into the system and how much people are using. Demand may rise in the morning and evening, while in many areas it is lower at night. The tank gives the system a degree of reserve instead of requiring everything to be adjusted immediately to peak demand.
The U.S. Geological Survey (USGS) describes the simple principle: water is pumped into a tower or elevated tank and can then flow through pipes to homes by gravity. This type of supply is also familiar in various forms from reservoirs located on hillsides. A tower itself is therefore not necessary everywhere that suitable naturally elevated terrain is available.
The U.S. Environmental Protection Agency (EPA) also explains that elevated storage tanks help meet peak demand and balance pressure in the network. Depending on their design, they may temporarily support supply even if a pump fails. This does not mean, however, that every tower can provide water indefinitely or operate without other equipment.
Why is the tank high above the ground?
The key is gravitational pressure. The greater the height difference between the water level in the tank and the point of use, the greater the hydrostatic pressure that may be available. The actual pressure in your home is also affected by pipe losses, differences in street elevation, neighbouring demand, regulating equipment, and the division of the network into pressure zones.
A simplified rule says that a 10-metre column of water corresponds to roughly one bar of pressure. This is an approximate physical value, not a guarantee of a particular pressure at the tap. If you live above the level of the tank, another technical solution may be needed. Excessively high pressure is not automatically beneficial either: the distribution system must be designed safely.
A tank on a column raises the water level even on flat land where no hill is available. Where a suitable hill exists, water utilities can use a conventional ground-level reservoir at a sufficient elevation. Height is therefore crucial for pressure, but the specific shape of the tank does not itself create pressure.
Why do some tanks look like giant balls?
Water-tower manufacturers offer several structural types. Landmark Structures describes the so-called spheroid elevated tank, a spheroid tank supported by a single column. The structure has fewer exposed load-bearing elements than some tanks on multiple legs and allows access equipment to be placed inside the support.
A sphere is a geometrically compact shape: among enclosed solids, it has the smallest surface area for a given internal volume. However, this property does not mean that a real spherical water tower is the cheapest option in every town. Its construction includes welding, a support structure, reinforcement, protective coatings, maintenance access, and operational requirements.
Many structures that look like a ball from a distance are actually spheroid or consist of several curved sections. This is why manufacturers use the term spheroid, rather than always using sphere. Their rounded appearance may result both from practical design and from an architectural requirement that the tank should not look like an industrial container in the middle of a built-up area.
Is a spherical water tower better than a conventional cylinder?
There is no single clear answer. A technical guide from STI/SPFA notes that operating conditions, topography, required capacity, and different structural designs should be compared when selecting a water tank. In practice, a ground-level reservoir, a tall cylindrical water tower, a tank on multiple supports, or a spheroid type on a single column may be appropriate.
A spheroid tank has aesthetic and structural advantages, but manufacturing its curved plates may be more demanding. A large cylindrical tank on a hill, on the other hand, may offer a simpler solution where suitable terrain already exists. Wind resistance, foundation loads, corrosion protection, and service access also matter.
For this reason, a marketing claim that one shape is “best” is not enough. A water-supply project is not assessed from a photograph. It considers capital and operating costs over its lifetime, pressure requirements, and how much water the tank must hold and for how long.
Can water flow from the ball even without electricity?
If the tank is sufficiently full, the pipes are unobstructed, and the points of use are within the correct pressure zone, water can flow by gravity for a certain time without a continuously operating pump. This is one reason elevated storage has practical value. It does not, however, mean that the water utility is completely energy-independent.
The water first has to be lifted to that height, usually by pumping. Electricity may also be needed for the treatment plant, network control, and other parts of the system. During a power outage, actual endurance depends on the stored volume, the number of users, and emergency measures. If the tank is empty or a pipe is damaged, its impressive appearance will not solve the problem.
A storage tank is not a substitute for water-quality control either. The EPA warns that long water residence times, sediment, biofilm, or damaged openings can pose hygiene risks. The operator must therefore ensure regular inspections, suitable circulation, and cleaning, regardless of whether the tank is spherical or cylindrical.
What is inside a single-column tank?
It is not a habitable room or a public viewing platform. The main section is used to store water, while pipes and technical access may run through the support. The exact arrangement depends on the manufacturer and the specific structure. Some types have technical stairs or a ladder, entrances, and maintenance equipment, but they are not generally open for unrestricted access.
Ladders, platforms, vents, or antennas may be visible on the tank, but not everything in an image must be directly related to water. Local water utilities may also use the structure separately for other technical equipment if permitted by the design and safety rules. Without documentation for a specific structure, however, it is impossible to determine exactly what is hidden inside.
How can you tell a spherical water tower from a similar industrial tank?
The ball shape alone is not enough to be certain. Spherical storage tanks are also used in industry for other substances, and their technical design is often different. A water tower is typically connected to a water-supply network, has appropriate markings, and often stands in an elevated or strategically selected location. By contrast, a tank at a chemical facility should not be labelled a drinking-water reservoir based on its shape alone.
If you are interested in a specific structure in your town, the water utility or municipal documentation is often a reliable source. This can reveal its actual purpose, capacity, and history without making assumptions from a photograph.
The key distinction is this: the height of a water tower helps supply the distribution network with pressurised water, while a spheroid shape is one option for constructing a practical tank. Its suitability is determined by the entire water-supply system, not geometry alone.
Sources
- U.S. Geological Survey – A water tower stores water for a town's use (gravity and water supply) – https://www.usgs.gov/media/images/a-water-tower-stores-water-a-towns-use
- U.S. Environmental Protection Agency – Revised Total Coliform Rule Assessments and Corrective Actions Guidance Manual (elevated tanks, pressure, and reserve capacity) – https://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=P100NUZO.TXT
- Landmark Structures – Spheroid Elevated Tanks (single-support tank construction) – https://www.teamlandmark.com/what-we-do/tank-storage-solutions/spheroid-elevated-tanks/
- Steel Tank Institute/Steel Plate Fabricators Association – Steel Water Storage Tanks: A Selection Guide (choice of shape, operational and structural factors) – https://stispfa.org/resource/steel-water-storage-tanks-a-selection-guide/
Gabriel Čatár
I'm interested in everyday things we encounter but don't always understand. From technology and personal finance to practical guides and fascinating facts about the world. At Offpitch, I focus on topics worth exploring in greater depth, checking the facts and explaining them in a clear, accessible way. My goal is to make sure readers take away something useful from every article.
