Some submersible pumps can also be used externally because they are cooled and lubricated by the water that they pump. They shouldn't overheat if they are stored in a dry, well-ventilated place out of direct sunlight.

Pumps of ten watts or more are often fitted with thermal overload cut-outs that trip at around 38 degrees centigrade and will survive overheating. However, smaller pumps without cut-outs should trip a circuit breaker before they begin to melt.

The advantage of dual-use pumps is that they don't need a weatherproof chamber, but you might want to place them inside a box for sound insulation. If you do this, take extra care because there is no cooling device beyond that of the water flowing through, and these pumps should be given plenty of ventilation.