The present invention describes an apparatus (1) and a method for use in regulation of the energy potential in a fluid column located within a pipeline (13), the apparatus (1) including two impellers (2), either one including a rotatable shaft (6) which is provided with a plurality of vanes or plate-shaped blades (8), the impellers (2) being disposed in a housing (4) which constitutes a portion of the pipeline (13), the apparatus (1) communicating with a load (19, 21) and/or an energy source, so that the impellers (2) of the apparatus (1) are arranged to influence the movement of the fluid column within the pipeline (13), the apparatus (1) being arranged to receive the fluid column between the shafts (6) of the impellers (2), the centre axis of said shafts (6) being substantially in the same plane as wall portions of the housing (4) upstream and downstream of the vanes, whereby the rate of the fluid column through the apparatus substantially corresponds to the rate of the fluid column immediately upstream and/or downstream of the impellers (2) of the apparatus (1).