Which of the following services typically utilizes a positive displacement pump?

Positive displacement pumps are designed to move fluid by trapping a fixed amount and forcing that volume into the discharge pipe. This makes them particularly effective in applications where a constant flow rate and pressure are required, regardless of the system's conditions.

In boiler fuel oil pump systems, these pumps are commonly used because they can handle the viscous nature of fuel oil, ensuring a steady and reliable supply to the boiler. This is critical in maintaining the efficiency and safety of the heating process. The positive displacement mechanism minimizes fluctuations in pressure and flow rate, which is essential for the uniform combustion of fuel in boilers.

In contrast, while other systems such as water supply and wastewater treatment do utilize pumps, they typically rely on centrifugal pumps, which are better suited for moving large volumes of fluid at lower pressures. Shower systems, too, typically use centrifugal pumps designed for high flow rates rather than the consistent pressures provided by positive displacement pumps. Therefore, the use of positive displacement pumps in a boiler fuel oil system is indicative of their specific function and efficiency in high-pressure applications.