A submersible pump is a pump which has a sealed motor coupled to the pump body. The whole assembly is submerged
or partially submerged in the fluid to be pumped. The main advantage of this type of pump is that it prevents pump decay, a problem associated with a height difference between a pump and the fluid surface. Pump decay results in damage to the pump and occurs where pressure at the pump inlet is too low causing the fluid to vaporize inside the pump body. Submersible pumps also are easily compared to other alternatives.
In a sewage pump system there are mechanical seals used to prevent the fluid being pumped from entering the motor and causing a short circuit. The pump can either be connected to a pipe, flexible hose or lowered down guide rails or wires so that the pump sits on a coupling, thereby connecting it to the delivery pipe-work.