A booster valve comprising a housing having a signal port, an actuator port, a supply port, and an exhaust port disposed therein. Disposed within the housing are upper and lower plugs. The upper and lower plugs and the housing collectively define a signal chamber which fluidly communicates with the signal port, an actuator chamber which fluidly communicates with the actuator port, and a supply chamber which fluidly communicates with the supply port. The upper and lower plugs are selectively moveable between neutral, delivery and discharge positions. When in the neutral position, the actuator chamber is fluidly isolated from both the supply chamber and the exhaust port. When in the delivery position, the actuator chamber fluidly communicates with the supply chamber but is fluidly isolated from the exhaust port. Finally, when in the discharge position, the actuator chamber fluidly communicates with the exhaust port but is fluidly isolated from the supply chamber.