A valve including: a valve body having an inlet port, an outlet port in selective fluid communication with the inlet port by a main passageway through the valve, and a valve seat surrounding the main passageway; a valve member mounted in the valve body for movement between first and second positions respectively blocking and permitting flow through the valve seat, the valve member having a piston portion comprising a radially outer wall, the piston portion separating a control chamber upstream of the valve seat from a point downstream of the valve seat, and the valve member having a pilot orifice through the piston portion for bleeding off pressure from the control chamber to the point downstream of the valve seat; a plunger movable between a first position blocking flow through the pilot orifice and a second position allowing flow through the pilot orifice; and a bleed orifice extending through the piston portion and in communication with the inlet port and the control chamber for allowing pressure from the inlet port to build up in the control chamber for urging the valve member in the first position when the plunger is in its first position, the bleed orifice disposed radially inwardly of the radially outer wall of the piston portion; characterised by a resilient biasing member connecting the valve member to the plunger so that, when the plunger is in its second position allowing flow through the pilot orifice, the resilient biasing member resiliently biases the valve member in its second position away from the valve seat and towards the plunger, permitting flow from the inlet port to the outlet port via the main passageway when there is low or no flow through the main passageway. a valve body having an inlet port, an outlet port in selective fluid communication with the inlet port by a main passageway through the valve, and a valve seat surrounding the main passageway; a valve member mounted in the valve body for movement between first and second positions respectively blocking and permitting flow through the valve seat, the valve member having a piston portion comprising a radially outer wall, the piston portion separating a control chamber upstream of the valve seat from a point downstream of the valve seat, and the valve member having a pilot orifice through the piston portion for bleeding off pressure from the control chamber to the point downstream of the valve seat; a plunger movable between a first position blocking flow through the pilot orifice and a second position allowing flow through the pilot orifice; and a bleed orifice extending through the piston portion and in communication with the inlet port and the control chamber for allowing pressure from the inlet port to build up in the control chamber for urging the valve member in the first position when the plunger is in its first position, the bleed orifice disposed radially inwardly of the radially outer wall of the piston portion; characterised by a resilient biasing member connecting the valve member to the plunger so that, when the plunger is in its second position allowing flow through the pilot orifice, the resilient biasing member resiliently biases the valve member in its second position away from the valve seat and towards the plunger, permitting flow from the inlet port to the outlet port via the main passageway when there is low or no flow through the main passageway.