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A fluid delivery system comprising a pump arranged to draw fluid, in use, from a reservoir (1) and dispense it through a dispensing tube (4), the pump comprising a cylinder (21) in which a piston (22) is reciprocally movable; an inlet into the cylinder; a one-way inlet valve (17) for controlling flo

A fluid delivery system comprising a pump arranged to draw fluid, in use, from a reservoir (1) and dispense it through a dispensing tube (4), the pump comprising a cylinder (21) in which a piston (22) is reciprocally movable; an inlet into the cylinder; a one-way inlet valve (17) for controlling flow through the inlet; an outlet from the cylinder and leading to the dispensing tube; and an outlet valve (27) controlling flow through the outlet, wherein the piston is arranged to selectively contact the outlet valve to maintain it open during the initial portion of its downstroke and to allow it to close for the remainder of the downstroke.

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1. A fluid delivery system comprising: a pump arranged to draw fluid, in use, from a reservoir and dispense it through a dispensing tube, the pump comprising a cylinder in which a piston is reciprocally movable;an inlet into the cylinder;a one-way inlet valve for controlling flow through the inlet;a

1. A fluid delivery system comprising: a pump arranged to draw fluid, in use, from a reservoir and dispense it through a dispensing tube, the pump comprising a cylinder in which a piston is reciprocally movable;an inlet into the cylinder;a one-way inlet valve for controlling flow through the inlet;an outlet from the cylinder and leading to the dispensing tube; andan outlet valve located in the outlet and having a tip proximal the piston and movable into the cylinder beyond an initial portion of the downstoke of the piston, the outlet valve controlling flow through the outlet, and in a closed position when the tip of the outlet valve enters the cylinder, and in an open position when the tip of the outlet valve is obstructed from entering the cylinder,wherein both the inlet valve and the outlet valve are simultaneously open during the initial portion of the downstroke of the piston, the outlet valve open as the outlet valve is prevented from the closed position while the tip of the valve element is obstructed from entering the cylinder by a side wall of the piston in proximity to the outlet, and the inlet valve open as the downstoke of the piston re-opens the inlet valve;wherein while both the inlet valve and the outlet valve are open, fluid from a reservoir is drawn through the inlet, and at least a portion of fluid in the dispensing tube is drawn back to the cylinder through the outlet; andwherein the piston is to release the outlet valve to close for the remainder of the downstroke when the tip of the outlet valve is no longer obstructed to enter the cylinder by the side wall of the piston. 2. A system according to claim 1, wherein the outlet valve comprises a valve element positioned in an orifice at a side wall of the cylinder and biased to a closed position in which the valve element projects into the cylinder, the valve element being arranged to be opened by the piston moving in the cylinder past the outlet valve element and pushing the projecting part of the valve element out of the cylinder against the action of the biasing force. 3. A system according to claim 1, wherein the inlet valve comprises a floating valve element. 4. A system according to claim 1, wherein the dispensing tube comprises an upward portion extending away from the piston leading into a curved transitional portion, the curved transitional portion leading to a generally downwardly facing outlet. 5. A system according to claim 4, wherein the piston is configured to suck the liquid back to a location, which is back beyond the point where it could flow out of the outlet under gravity. 6. A dispenser for soap and the like having a replaceable reservoir of liquid, the reservoir having an outlet orifice at its lower end and a reservoir outlet valve for controlling the flow from the outlet, a base unit having a spigot which engages with the outlet in the reservoir to open the valve, the base unit being provided with a fluid delivery system according to claim 1, the one-way inlet valve being arranged to control the flow of liquid through the spigot and into the cylinder. 7. A dispenser according to claim 6, wherein the base unit is provided with a motor, a control circuit and a sensor to detect the presence of movement in the vicinity of the dispensing tube, the control circuit being arranged to drive the motor to move the piston when movement is detected. 8. A dispenser according to claim 6, the dispenser being a free standing unit. 9. A dispenser according to claim 8, wherein the dispenser is battery powered. 10. A fluid delivery system comprising: a pump arranged to draw fluid, in use, from a reservoir and dispense it through a dispensing tube, the pump comprising a cylinder in which a piston is reciprocally movable;an inlet into the cylinder;a one-way inlet valve for controlling flow through the inlet;an outlet from the cylinder and leading to the dispensing tube; andan outlet valve controlling flow through the outlet, wherein the piston is arranged to selectively contact the outlet valve to maintain it open during the initial portion of its downstroke, while simultaneously opening the inlet valve, such that the inlet valve is also open during the initial portion of the piston's downstroke, to permit the flow of fluid into the cylinder, and to release the outlet valve to close for the remainder of the downstroke;wherein the outlet valve comprises a valve element positioned in an orifice at a side wall of the cylinder and biased to a closed position in which the valve element projects into the cylinder, the valve element being arranged to be opened by the piston moving in the cylinder past the outlet valve element and pushing the projecting part of the valve element out of the cylinder against the action of the biasing force;wherein the inlet valve comprises a floating valve element;wherein the dispensing tube comprises an upward portion extending away from the piston leading into a curved transitional portion, the curved transitional portion leading to a generally downwardly facing outlet; andwherein the piston is configured to suck the liquid back to a location, which is back beyond the point where it could flow out of the outlet under gravity. 11. A dispenser for soap and the like having a replaceable reservoir of liquid, the reservoir having an outlet orifice at its lower end and a reservoir outlet valve for controlling the flow from the outlet, a base unit having a spigot which engages with the outlet in the reservoir to open the valve, the base unit being provided with a fluid delivery system according to claim 10, the one-way inlet valve being arranged to control the flow of liquid through the spigot and into the cylinder.