We cannot solve our water issue by relying on pumps. It is true that in very small water systems consisting exclusively of residential customers, pumps can be sized to provide peak-hour demand and firefighting volume. In fact, that is exactly how our small Black Oak pump station is designed to work. But this station only serves a very small population. In large systems, meeting peak-hour demand and firefighting volume would require prohibitively large and expensive pumps.
Under standard water engineering practice, pumps are designed to meet the maximum-day demand, and tank water storage is designed to supply the peak-hour demand above the capacity of the pumps. To instead design a system that relies on pumps to meet the peak-hour demand would be complex, requiring more pumps to supply a greater range of flows. Not only would we need more pumps, but the pumps would need to be more powerful. Furthermore, system piping would need to be significantly upsized, all of the electrical systems in the pump station would need to be increased, the capacity of the emergency generator would need to be increased, and the control systems for the additional pumps would need to be upgraded. Using pumps rather than tank storage to meet peak-hour demand would be complicated and less reliable than using water tanks with adequate storage capacity. Furthermore, the Insurance Services Office, which sets the Town’s insurance rates, does not consider reliance on pumps alone to be a suitable or reliable provider of water for large fire flows. The State also requires that water needed for firefighting come from water storage.
Engineering practice and state guidance both dictate that pumps be designed to meet only the maximum-day demand. Water demands that are higher than that, such as peak-hour demand, should come from water storage. Our pumps were designed so that one pump meets average-day demand, and two pumps meet maximum-day demands. The third pump is a backup pump.
Besides being the economical way to provide water pressure, storage from a water tank of adequate size and elevation harnesses the power of gravity, which is much more reliable than electric pumps. Gravity works even when the power goes out. That is why tanks of adequate size and height are the standard, tried and true approach to the provision of municipal water. As climate change increases our need for resilient systems in the face of ever-fiercer storms, a water system based on the power of gravity rather than the electrical grid is by far the wiser approach.