Abstract: A fluid storage tank utilizing a shear seal in which a leak proof static shear seal covers the entire head of the piston of the storage tank requiring only a single fluid tight seam to seal off the fluid storage chamber from the remainder of the storage tank. The shear seal has a circumferential notch located proximate to its outer periphery which permits the shear seal to rupture along a predetermined path. Elastomeric annular seals on the piston provide a dynamic seal to prevent the fluid from leaking while the piston is moving to eject the stored fluid. The head of the piston flattens any protruding portions of the ruptured shear seal against the walls of the storage tank.