A valve for a pressure vessel of an automatic fire extinguishing system comprises a valve housing with a valve output opening for connecting an extinguishing line, a valve input opening for connecting the valve to the pressure vessel, a valve seat arranged between the valve output opening and the valve input opening, a low pressure chamber for connecting a triggering device and a high pressure chamber connectable with the low pressure chamber, wherein arranged in a the valve housing is a closing piston comprising a valve seat seal, which can be moved between a closing piston closed position and a closing piston open position, a pressure control unit in pressure connection with the valve input opening and the low pressure chamber for controlling the low pressure in the low pressure chamber relative to a vessel pressure of the pressure vessel and a control piston which can be moved between a control piston closed position and a control piston open position, wherein the closing piston is arranged in the closing piston closed position with the valve seat seal on the valve seat in a fluid-tight manner so that the valve output opening is sealed relative to the valve input opening, wherein the closing piston is arranged in the closing piston open position spaced apart from the valve seat, so that the valve output opening and the valve input opening are in pressure connection, wherein the control piston in the control piston closed position seals a pressure channel between the high pressure chamber and the low pressure chamber in a fluid-tight manner, and wherein the control piston in the control piston open position releases the pressure channel, so that the high pressure chamber and the low pressure chamber are in pressure connection.