A discharge duct for discharging pump water from a supply reservoir defined by a first minimum water level and a supply reservoir floor to an operatively higher located delivery reservoir defined by a second minimum water level and the delivery reservoir floor, the discharge duct being defined by an inlet at one end of the discharge duct in communication with the outlet orifice of a conventional pumping device fitted at the supply reservoir; an outlet at the other end of the discharge duct, in the operative configuration of the discharge duct, being below the second minimum water level.