Irrigation pumps are the heart of a nursery irrigation system. Pumps can be either rotodynamic e.g. centrifugal pumps, or positive displacement e.g. helical-rotor pumps. Most nursery irrigation systems require high efficiency and high pressures (head) which usually limits pumps suitable to these systems to rotodynamic pumps, but in situations where pump discharges are less than 2 litres per second, positive displacement pumps may be used e.g. misting systems.