The invention relates to a hydraulic circuit provided with at least one hydraulic power machine (2, 4) connected to a low-pressure circuit (6) and to a high-pressure circuit (10) transmitting said power, wherein the machine is provided with a drain which allows internal leaks in the casing thereof to flow towards a low-pressure accumulator (8) or a vessel at atmospheric pressure, said circuit comprising an intake pipe (30) connecting the low-pressure circuit (6) to the casing of the machine, and an outlet pipe (36) forming the drain receiving the flow from the intake pipe in order to guide same towards the vessel (8), including a heat exchanger (42) and a filter (44) forming the fluid treatment elements for the entire hydraulic circuit, said circuit also comprising a means for monitoring the flow (40) in the intake and outlet pipes.