A single-stage centrifugal pump has only one impeller and is used for applications that require low-pressure pumping. A multistage centrifugal pump has multiple impellers and can be used for high-pressure applications. Multistage pumps are more energy-efficient, but they also have higher installation and maintenance costs. Vertical multistage centrifugal pumps have a vertical shaft where the stages are stacked on top of each other. Clearances are small in these types of pumps, so they work best for clean water applications.