Look around the rooftops of many cities and you’ll see wooden water towers. New York has thousands of them.
The reason is simple and often overlooked:
In the morning, when every resident of the building is preparing for the day, there’s a need for thousands of gallons of water under high pressure. Providing that much power via a pump is expensive, noisy and difficult to maintain.
The system in use, on the other hand, takes two or three hours to refill the tank, using reliable, quiet and cheap small pumps. After that, gravity is all that’s needed.
Adding a reservoir to a high-demand system creates slack, resilience and efficiency.
Too often, foolish short-term profit seekers forget this, and use up what’s in the reservoir without keeping future reserves in mind.