Pressure reducer (10) having a housing (11) with a valve (12) positioned in said housing (11), wherein in closed position the valve (12) separates an inlet pressure chamber (13) of the housing (11) from an outlet pressure chamber (14) of the housing (11), and in open position connects the inlet pressure chamber (13) and the outlet pressure chamber (14), wherein the valve (12) has a diaphragm (16) acting on a valve tappet (15), on which diaphragm, by providing a pressure reducing function, a spring force of a spring element (17) acting in the opening direction of the valve (12) acts on the one hand and a force that is a function of the pressure prevailing in the outlet pressure chamber (14) acting in the closing direction of the valve (12) acts on the other hand, wherein the valve (12) has, attached to the valve tappet (15), a valve body (21) which, in closed position, bears against a valve seat (22) in a sealing manner and which in open position is raised off the valve seat (22), and wherein the spring element (17) is arranged between spring plates (18, 19), namely between a spring plate (18) facing the diaphragm (16) and a spring plate (19) facing away from the diaphragm (16). A sensor (27) for detecting leakage is integrated into the pressure reducer.