A pressure-relief assembly for adjusting pressure within a washing chamber of a washer, said pressure-relief assembly comprised of: a housing having an opened upper end and an internal cavity configured to communicate with a washing chamber of a washer, said opened upper end having a predetermined cross-section; and a valve assembly movable relative to said opened upper end of said housing between one of two opened positions and a closed position, said valve assembly having: a first plate section dimensioned to overlay and cover said opened upper end of said housing, said first plate section having an opening extending therethrough; a second plate section dimensioned to overlay said first plate section, said second plate section being movable relative to said first plate section between a closed position wherein said second plate section overlays and covers said opening in said first plate section and an open position wherein said second plate section is spaced from said first plate section; characterized by the valve assembly further having: an air cylinder having a cylinder housing, and a piston rod with a piston and a biasing element biasing said piston and piston rod, wherein said cylinder housing is connected to said first plate section, and said second plate section is connected to a free end of said piston rod, such that said second plate section is movable relative to said first plate section, and said biasing element biases said second plate section toward a closed position relative to said first plate section, wherein said second plate section overlays and covers said opening in said first plate section; and a guide section for guiding movement of said valve assembly relative to said opened upper end of said housing, said guide section including a cylindrical inner bore, wherein said cylinder housing is movable within said inner bore. a housing having an opened upper end and an internal cavity configured to communicate with a washing chamber of a washer, said opened upper end having a predetermined cross-section; and a valve assembly movable relative to said opened upper end of said housing between one of two opened positions and a closed position, said valve assembly having: a first plate section dimensioned to overlay and cover said opened upper end of said housing, said first plate section having an opening extending therethrough; a second plate section dimensioned to overlay said first plate section, said second plate section being movable relative to said first plate section between a closed position wherein said second plate section overlays and covers said opening in said first plate section and an open position wherein said second plate section is spaced from said first plate section; characterized by the valve assembly further having: an air cylinder having a cylinder housing, and a piston rod with a piston and a biasing element biasing said piston and piston rod, wherein said cylinder housing is connected to said first plate section, and said second plate section is connected to a free end of said piston rod, such that said second plate section is movable relative to said first plate section, and said biasing element biases said second plate section toward a closed position relative to said first plate section, wherein said second plate section overlays and covers said opening in said first plate section; and a guide section for guiding movement of said valve assembly relative to said opened upper end of said housing, said guide section including a cylindrical inner bore, wherein said cylinder housing is movable within said inner bore. a first plate section dimensioned to overlay and cover said opened upper end of said housing, said first plate section having an opening extending therethrough; a second plate section dimensioned to overlay said first plate section, said second plate section being movable relative to said first plate section between a closed position wherein said second plate section overlays and covers said opening in said first plate section and an open position wherein said second plate section is spaced from said first plate section; characterized by the valve assembly further having: an air cylinder having a cylinder housing, and a piston rod with a piston and a biasing element biasing said piston and piston rod, wherein said cylinder housing is connected to said first plate section, and said second plate section is connected to a free end of said piston rod, such that said second plate section is movable relative to said first plate section, and said biasing element biases said second plate section toward a closed position relative to said first plate section, wherein said second plate section overlays and covers said opening in said first plate section; and an air cylinder having a cylinder housing, and a piston rod with a piston and a biasing element biasing said piston and piston rod, wherein said cylinder housing is connected to said first plate section, and said second plate section is connected to a free end of said piston rod, such that said second plate section is movable relative to said first plate section, and said biasing element biases said second plate section toward a closed position relative to said first plate section, wherein said second plate section overlays and covers said opening in said first plate section; and a guide section for guiding movement of said valve assembly relative to said opened upper end of said housing, said guide section including a cylindrical inner bore, wherein said cylinder housing is movable within said inner bore.