A Flow control valve for a pump suction line permitting flow from an alternate source in the event of partial or complete blockage of a main source. The valve includes a valve housing having a main inlet port at one end, on auxiliary inlet port at its other end and a suction port between the inlet ports. Flow responsive valves are provided at the inlet ports and the valves are spring biased by springs which allow normal flow through the main inlet port. If the main inlet port is blocked the auxiliary port is opened. A flap valve is actuated by flow through the auxiliary port to close the auxiliary port and to create hydrostatic pressure between the blockage and the main inlet port to thereby dislodge the blockage.