In this work, injector regulating valve and Pelton turbine impeller has been numerically and analytically designed and simulated. The impeller of the Pelton turbine was added on the shaft of a high pressure multistage pump which is used in sea water Reverse Osmose (RO) desalination package to recover a part of input power from rejected flow return back after filter unit. Turbulent flow through the regulating valve for many outlet injector diameters has been numerically simulated to obtain head loss. For the point of operation, dimension of turbine impeller calculated using turbomachinery relations and some experimental data in order to synchronize as much as possible with the pump. The exact point of operation for the pump, turbine and injector obtained by intersecting performance curves of pump and turbine. In order to investigate the results, the full-scale Pelton turbine and regulating valve manufactured with the material of duplex and installed on the pump. Performance test on the site shown about 26% decrease in input power. Because of the affinity relation for turbomachinery, the results can be validated for other point of operation due to change in pump speed. (C) 2019 Elsevier Ltd. All rights reserved.