A system comprising: - a plumbing circuit having an inlet port for receipt of pressurized gas and plumbing that includes a plurality of valves, the plumbing circuit comprising: - a product tank; - a first fluid circuit, located upstream of a highest point of the plumbing circuit, the first circuit comprising: - a centrifugal pump coupled on a downstream end of the centrifugal pump to a main delivery line; - a sump valve and a product recovery upstream valve coupled to an upstream end of the centrifugal pump; and - a recirculatory valve coupled to the product tank, the product recovery upstream valve and a recirculatory line; - a second fluid circuit, located downstream of a highest point of the plumbing circuit, the second circuit, comprising: - a boom plumbing assembly; - a plurality of nozzles coupled to the boom plumbing assembly; and - a serial arrangement of a main shut-off valve, - a center boom feed valve, and - a product recovery rear manifold valve, - the main shut-off valve coupled to the main delivery line, - the product recovery rear manifold valve coupled to the plurality of nozzles, and - the center boom feed valve and the product recovery rear manifold valve coupled to the recirculatory line; and - one or more controllers that are operable to perform a method comprising: - opening and closing a plurality of valves of the plumbing circuit to control, under influence of a pressurized gas that is injected into an air inlet in the boom plumbing assembly, - a flow of liquid product through plumbing of the first fluid circuit when the centrifugal pump is temporarily inactive and a flow of liquid product through plumbing of the second fluid circuit, including through the recirculatory line; and, - dispensing the liquid product of the first and second fluid circuits (36,38) to either the product tank or through the plurality of nozzles based on the flows. - a plumbing circuit having an inlet port for receipt of pressurized gas and plumbing that includes a plurality of valves, the plumbing circuit comprising: - a product tank; - a first fluid circuit, located upstream of a highest point of the plumbing circuit, the first circuit comprising: - a centrifugal pump coupled on a downstream end of the centrifugal pump to a main delivery line; - a sump valve and a product recovery upstream valve coupled to an upstream end of the centrifugal pump; and - a recirculatory valve coupled to the product tank, the product recovery upstream valve and a recirculatory line; - a second fluid circuit, located downstream of a highest point of the plumbing circuit, the second circuit, comprising: - a boom plumbing assembly; - a plurality of nozzles coupled to the boom plumbing assembly; and - a serial arrangement of a main shut-off valve, - a center boom feed valve, and - a product recovery rear manifold valve, - the main shut-off valve coupled to the main delivery line, - the product recovery rear manifold valve coupled to the plurality of nozzles, and - the center boom feed valve and the product recovery rear manifold valve coupled to the recirculatory line; and - one or more controllers that are operable to perform a method comprising: - opening and closing a plurality of valves of the plumbing circuit to control, under influence of a pressurized gas that is injected into an air inlet in the boom plumbing assembly, - a flow of liquid product through plumbing of the first fluid circuit when the centrifugal pump is temporarily inactive and a flow of liquid product through plumbing of the second fluid circuit, including through the recirculatory line; and, - dispensing the liquid product of the first and second fluid circuits (36,38) to either the product tank or through the plurality of nozzles based on the flows. - opening and closing a plurality of valves of the plumbing circuit to control, under influence of a pressurized gas that is injected into an air inlet in the boom plumbing assembly, - a flow of liquid product through plumbing of the first fluid circuit when the centrifugal pump is temporarily inactive and a flow of liquid product through plumbing of the second fluid circuit, including through the recirculatory line; and, - dispensing the liquid product of the first and second fluid circuits (36,38) to either the product tank or through the plurality of nozzles based on the flows.