A pressure discharge valve for storage tanks on land or trucks including a valve body having a through hole therein adapted to mate and communicate with a through hole in a wall of the storage tank, a first vent means comprised of a eutectic composition which automatically provides a partial release of storage tank liquid at a first predetermined temperature lower than critical combustion and/or explosive temperatures of liquid in the storage tank, to provide a visual signal and warning to firefighters of these hazardous conditions, and a second vent means comprised of a eutectic composition to automatically vent liquid in the storage tank through the hole in the valve body when the liquids therein reach a predetermined critical temperature. In addition, the pressure discharge valve preferably comprises a eutectic solder material disposed between the valve body and the second vent means, which changes phase (i.e., reaches its eutectic point) below the eutectic point of the second vent means, thereby providing a lubricant between the plug and the valve body.