A fluid flow control system in which a vortex valve is combined in series with a non-fluidic control valve. The non-fluidic control valve is upstream of the vortex valve and is so arranged that small changes in its state control the operation of the vortex valve, which provides the major control over the flow of the fluid. Erosion in the non-fluidic valve due to abrasion or cavitation in the non-fluidic valve is thereby reduced.