Abstract: The invention relates to a heat pump. It relates to a heat pump which, in a primary circuit, comprises a compressor (10), a condenser (12) forming a heat exchanger between the refrigerating fluid and the swimming pool water, an expander (14) and an evaporator (16) forming a heat exchanger between the external surroundings and the refrigerating fluid. The condenser (12) comprises two heat exchange circuits and the heat pump comprises a pressure sensor (18), a member for switching the circulation of the refrigerating fluid between states in which it is circulated in just one or in at least two of the heat exchange circuits, and a member for controlling the switching member according to the value of the signal from the sensor (18). Application to the heating of swimming pool water.