Abstract: A carpet cleaning system that delivers heated cleaning water from a truck to a carpet cleaning apparatus and an improved waste disposal tank designed to receive the waste water and deposit it into the toilet or sewer drain when the disposal tank is full. The disposal tank is divided into an upper primary recovery tank and a lower recovery tank. A main vacuum line and waste water return line are connected to the primary recovery tank. Disposed between the primary and secondary recovery tanks is a first check valve that controls the flow of waste water therebetween. Connected over the outlet port on the secondary recovery tank is a second check valve that operates in opposite direction to the first check valve. Attached to the secondary recovery tank is an air control valve that controls the flow of air from the primary recovery tank or the outside air into the secondary recovery tank. A timer or a float valve is connected to the air control valve to selectively control its operation.