Abstract: The regulator comprises an enveloping body with a closure diaphragm on which a spring acts, said body comprising an entrance for the pressure liquid and an exit toward the pressure liquid application apparatus, characterised in that, at the bottom, the body comprises a closure plug with a graduable axial position for achieving a depressurisation position or free passage position, and, at the top, the compression spring on the diaphragm abuts against a flange of an asymmetrical intermediate body, of which the inversion brings about the two different preloading positions of the spring providing two regulator adjustment pressures.