A pumping circuit for fluid of an ink circuit in a continuous inkjet printer, including a diaphragm pump, an inlet circuit having an inlet conduit into the pump for the fluid to be pumped, an outlet conduit for the fluid pumped by the pump, the pumping circuit including a back-flow line which removes, from the outlet of the pump, part of the pumped fluid and returns it to the inlet circuit of fluid to be pumped, at least one singular restriction being arranged on the path of the fluid in the back-flow line, and the back-flow line regulating the pressure and the flow rate of the fluid at the outlet of the pump.