Drain pump (submersible)

A submersible drain pump is a sealed electrically driven pump installed inside a sump or wet well to lift wastewater or surface water to a higher level. Pumps used for foul flows include cutter or vortex impellers to handle solids, while clean water and surface water pumps use simpler designs. Selection follows duty point calculations of flow and head, with margins for inflow surges. Installation must comply with BS EN 12050 for wastewater lifting plants and BS 7671 for the electrical supply, and the pump should be supplied via a residual current device on a dedicated circuit. Multi-residential and basement installations in London typically use twin pumps in duty and standby arrangement with high level alarms, so a single pump failure does not cause flooding.