The swirling flow generated in an elbow suction pipe of a centrifugal pump at partial discharges was studied and the results were compared with that generated in a straight suction pipe. Distribution of velocity may be considered to be nearly in symmetry about the pipe axis but the wall pressures measured at four taps in a section of the pipe spaced 90 deg. circumferentially show a considerable difference. The averaged value of the pressure is elevated by the centrifugal action of the swirling motion and the increase of pressure is affected considerably by the piping installation. The swirling flow due to a back flow from the impeller can not penetrate a 90 deg-elbow but some of it passes through a 45 deg-elbow, resulting in a markedly complex flow picture upstream of the elbow.