Abstract: A rotating flow pump such as a centrifugal pump is provided with a feed pump unit formed as an ejector. The feed pump unit comprises an inlet portion, a nozzle, and a diffuser arranged in succession, and the diffuser is connected to the inlet opening of the flow pump. The inlet portion, the nozzle, and the diffuser of the ejector are situated in a plane perpendicular to the shaft of the flow pump. The diffuser comprises an inner channel of a uniformly increasing flow cross section at least over part of its length. Furthermore the diffuser comprises an outer jacket situated substantially coaxially about the above channel. Thus the jacket is formed in such a manner that a substantially 180.degree. almost mushroom-shaped turning of the flow direction for the liquid flowing through the diffuser is obtained at the same time as a uniformly increasing flow cross section--seen in the flow direction--is obtained within the annular chamber between the channel and the jacket.