Abstract: A valve for use with a downhole pump, wherein the valve comprises a single moving part that in a first position forms only a first interface and in a second position forms only a second interface, each interface presenting a barrier that cannot be breached by fluid, whereby the first interface directs fluid to the production tubing only from the annulus and the second interface directs fluid to the production tubing only from the pump, the pump and annulus and production tubing are simultaneously interconnected by a chamber of the valve when the single moving part is between the first and second positions, each interface is maintained or broken depending on the fluid pressure differential across the associated interface, the single moving part moves between the first position and second position according to the fluid direction through the valve, characterised by each of the two interfaces being formed between a convex surface of the single moving part and a concave surface of a non moving part of the valve,