The drainage pump is used for draining pits and deep roadway underpasses, as well as for dewatering basements and courtyards subject to a flooding risk or groundwater. It is usually started automatically via float switches. The water to be handled may contain dirt and solids whose permissible particle size depends on the pump size and impeller.
The conventional pump design, see Fig. 1 Drainage pump,
where the pump is rigidly connected to an air-cooled flanged motor via a long support column, is being replaced more and more by submersible motor pumps. See Fig. 2 Drainage pump
In these latter machines, usually installed vertically, the motor situated above the pump (oil-filled for better cooling) is sealed by mechanical seals and shaft sealing rings. The chamber located between the sealing elements installed in pairs is filled with grease or oil.
The compact design makes the submersible motor pump a portable, transportable pump suitable for draining.