What is the term for a storage vessel that is uniform in diameter from top to bottom and falls between 20 and 80 feet in height?

The term that describes a storage vessel uniform in diameter from top to bottom and between 20 and 80 feet in height is referred to as a standpipe. A standpipe serves as a water storage and distribution mechanism, functioning to maintain adequate pressure in water supply systems.

Standpipes are typically cylindrical, allowing for easy construction and efficient water storage. Their height and uniform diameter allow them to store significant quantities of water while ensuring that the pressure at the delivery points remains stable. This makes them crucial for maintaining a constant water supply and helping to manage fluctuations in demand.

In contrast, elevated storage refers to tanks positioned at a height to create water pressure through gravity, which does not fit the dimensions and uniform shape described in the question. Ground storage typically involves water storage tanks located at ground level and may not maintain uniform diameters. Spherical storage involves tanks designed in a spherical shape, focusing more on structural integrity and storing under pressure rather than the specified uniform cylindrical form in the question.

Thus, the uniqueness of the standpipe with its specific dimensions and characteristics is why it is the correct term for the described storage vessel.