Abstract: A pump (10) has a housing (11), a base (12) and a flexible diaphragm (13) between the housing and the base. The diaphragm (13) and the base (12) define a driving chamber and the diaphragm (13) and the housing (11) define a pump chamber. The driving chamber is coupled to a pump driver adapted to direct fluid to and from the driving chamber to drive the diaphragm. The pump chamber is of generally conical form with its outlet (21) being located at the apex of the conical pump chamber and the inlet (22) being disposed at an angle inclined to the plane of the base of the conical pump chamber and being generally tangential to the outer portion of the base of pump chamber such that flow through the pump chamber is in the form of a continuous spiral vortex.