Regenerative pump having movable walls adjacent opposing faces of the impeller

A regenerative pump, comprising a housing defining a cavity having a fluid inlet and fluid outlet, and a channel extending between said fluid inlet and said fluid outlet, an impeller rotatably mounted within said cavity within the housing and having a plurality of vanes spaced angularly around the impeller axis and opening into said channel formed in the housing and a stripper block located between the inlet and the outlet to restrict direct flow of fluid between the outlet and inlet, in which said impeller is located in a central portion of said cavity, and first and second filler members define walls of the channel, are provided adjacent opposing faces of said impeller and are movable within the channel so as to vary the cross-section of said channel as measured in a first plane containing the axis of rotation of the impeller.