A valve apparatus and system is provided. The valve apparatus includes a housing having a fluid inlet and a fluid outlet. A support assembly is attached to the housing, the support assembly including a positioning chamber located over the outlet. A diaphragm assembly is moveably attached to the support assembly. The diaphragm assembly includes a piston having one end slideably mounted in the positioning chamber, and a diaphragm attached to the other end of the piston. A sealing element is located about a perimeter of the diaphragm, and a biasing element is arranged to contact the support assembly and the diaphragm assembly, thereby urging at least a portion of the sealing element against the fluid outlet, providing a fluid-tight seal.