A pneumatic conveying system is disclosed for conveying a granular product, such as grain, from a grain inlet device to a selected one of a plurality of grain bins or other storage vessels. The system includes a blower for forcing air under pressure into a conveyor piping system. A grain inlet device is located downstream from the blower. The piping system has a portion leading from the grain inlet to an inlet in a first one of the vessels. A discharge/bypass valve is connected to a portion of the piping system leading from the grain inlet so as to receive the granular product being conveyed therethrough with the valve having a discharge outlet for discharging the granular product into the vessel. The valve is installed on the vessel such that the discharge outlet is in communication with the interior of the vessel. The valve further has an inlet coupling operatively connected to the piping system and an outlet coupling operatively connected to another portion of the piping system downstream of the valve leading to another of the vessels. The valve has a sleeve movable between a discharge position in which the inlet coupling is disconnected from the outlet coupling such that the granular product is discharged from the piping system into the valve and then is discharged into the vessel and a by-pass position in which the inlet and outlet couplings are operatively connected so that the granular product is conveyed through the valve and into the piping system downstream from the valve.