Small submersible pumps are destined for pumping polluted waste water, e.g. faeces, sludge containing small-sized fragmented solids up to dia. 10 mm. The pumps are provided with a disintegrator (a grinder) for grinding solids being contained in a pumped stuff. There are overcurrent and thermal protection of klixon type built into the motor winding, so it is not possible to ensure another special protection of the pumps. On the customer’s request it is possible to deliver these pumps with and/or without a float.