A pressure regulator with a housing (41, 42), comprising - a housing lower part with an inlet and an outlet, - a housing upper part, - a membrane, which is clamped between the housing lower part and the housing upper part, - a bore, which leads from the outlet into a volume delimited by the membrane, - wherein the membrane is adapted so that it can be deviated, when liquid is urged back through the outlet and the bore beneath the membrane, whereby a volume of liquid may be collected inside the housing of the pressure regulator, - a valve assembly (49, 50) with a valve element, - wherein a connection between the inlet and the outlet through the valve element is controlled depending on the pressure at the outlet of the pressure regulator, - wherein the membrane is coupled to the valve element, - and wherein the valve assembly (49, 50) is adapted in order that the valve element is acted upon by a closing spring in the closing direction in order to control the pressure, and may be brought into an open position by the membrane, characterized in that - a first and a second bore (52, 53) are provided in the housing upper part, - wherein the bores (52, 53) are positioned in a way that compressed air may flow through the first bore into the housing upper part and may flow again out of the housing upper part through the second bore, - a sealing element, which is connected to the upper side of the membrane, and which is provided with a sealing surface, wherein the membrane is configured to be deflected by the liquid to such an extent, that the sealing element abuts against the upper side of the housing upper part and the sealing surface sealingly contacts the inner side of the second bore, whereby the outflow of compressed air from the housing upper part is prevented, - wherein the valve element may be brought by the membrane in the open position, when the pressure at the outlet drops below a value, which is defined by the force acting from above on the membrane, wherein the force is exerted by the compressed air, which flows through the first bore into the housing upper part and then flows again out through the second bore. - a housing lower part with an inlet and an outlet, - a housing upper part, - a membrane, which is clamped between the housing lower part and the housing upper part, - a bore, which leads from the outlet into a volume delimited by the membrane, - wherein the membrane is adapted so that it can be deviated, when liquid is urged back through the outlet and the bore beneath the membrane, whereby a volume of liquid may be collected inside the housing of the pressure regulator, - a valve assembly (49, 50) with a valve element, - wherein a connection between the inlet and the outlet through the valve element is controlled depending on the pressure at the outlet of the pressure regulator, - wherein the membrane is coupled to the valve element, - and wherein the valve assembly (49, 50) is adapted in order that the valve element is acted upon by a closing spring in the closing direction in order to control the pressure, and may be brought into an open position by the membrane, - a first and a second bore (52, 53) are provided in the housing upper part, - wherein the bores (52, 53) are positioned in a way that compressed air may flow through the first bore into the housing upper part and may flow again out of the housing upper part through the second bore, - a sealing element, which is connected to the upper side of the membrane, and which is provided with a sealing surface, wherein the membrane is configured to be deflected by the liquid to such an extent, that the sealing element abuts against the upper side of the housing upper part and the sealing surface sealingly contacts the inner side of the second bore, whereby the outflow of compressed air from the housing upper part is prevented, - wherein the valve element may be brought by the membrane in the open position, when the pressure at the outlet drops below a value, which is defined by the force acting from above on the membrane, wherein the force is exerted by the compressed air, which flows through the first bore into the housing upper part and then flows again out through the second bore.