Automatic inverter for 2 pumps, equipped with 2 inputs for pressure switches and 2 exits for the start of the pumps, it alternates the functioning of the pumps depending on the requests of the pressure switches. In case of simultaneous functioning, it introduces a 3 seconds delay between the start of the pumps in order not to overload the power supply system. The phase shift between the starts and forced march of 3 seconds allow the pumps not to damage caused by eventual continuous starts in case of damage to the expansion vessels.