Vessel filler system for diaphragm expansion vessels, having at least one pressurized-gas bottle which is filled with nitrogen, having valves, having a pressure reducer, having at least one manometer (6, 7, 8) and having a pressure hose, characterized in that - said vessel filler system comprises a compact, closed housing which has only a closable opening for receiving a pressurized-gas bottle and which otherwise cannot be opened by the user, thus allowing no access to the further structural components situated in the housing, - inserted into the housing, so as to be exchangeable and mounted in an impact-resistant manner, is the likewise compactly designed pressurized-gas bottle, which has a capacity of 0.5 1 to 1.5 1 and a filling pressure of approximately 150 - 200 bar and is completely enclosed by the housing, - wherein the pressurized-gas bottle is completely inserted, through the opening arranged in the housing at the bottom thereof, into a receptacle with lateral guides, said receptacle being closed by a releasably fastened cover, - and a connecting element to the gas-bottle valve for connection of the pressurized-gas bottle is arranged in an aligned manner in the housing at the upper end of said receptacle, - wherein the pressure reducer for the pressurized-gas bottle is configured for reducing the working pressure to approximately 5 - 10 bar and is fixedly installed, - wherein the pressure hose is fixedly connected to the housing and has a connection piece to the diaphragm expansion vessel, which connection piece is arranged at the free end of said pressure hose, - wherein the at least one manometer (6, 7, 8) is configured with readable displays arranged in the housing for the prevailing pressure of the pressurized-gas bottle, the working pressure after the pressure reducer and the pressure prevailing in the diaphragm expansion vessel, - actuation elements are provided on the housing for the feed and discharge of the gas into and out of the diaphragm expansion vessel. - said vessel filler system comprises a compact, closed housing which has only a closable opening for receiving a pressurized-gas bottle and which otherwise cannot be opened by the user, thus allowing no access to the further structural components situated in the housing, - inserted into the housing, so as to be exchangeable and mounted in an impact-resistant manner, is the likewise compactly designed pressurized-gas bottle, which has a capacity of 0.5 1 to 1.5 1 and a filling pressure of approximately 150 - 200 bar and is completely enclosed by the housing, - wherein the pressurized-gas bottle is completely inserted, through the opening arranged in the housing at the bottom thereof, into a receptacle with lateral guides, said receptacle being closed by a releasably fastened cover, - and a connecting element to the gas-bottle valve for connection of the pressurized-gas bottle is arranged in an aligned manner in the housing at the upper end of said receptacle, - wherein the pressure reducer for the pressurized-gas bottle is configured for reducing the working pressure to approximately 5 - 10 bar and is fixedly installed, - wherein the pressure hose is fixedly connected to the housing and has a connection piece to the diaphragm expansion vessel, which connection piece is arranged at the free end of said pressure hose, - wherein the at least one manometer (6, 7, 8) is configured with readable displays arranged in the housing for the prevailing pressure of the pressurized-gas bottle, the working pressure after the pressure reducer and the pressure prevailing in the diaphragm expansion vessel, - actuation elements are provided on the housing for the feed and discharge of the gas into and out of the diaphragm expansion vessel.