Micro hydro turbines are getting renewed research interest in recovering unused energy from systems like water supply pipelines, sewage treatment and transportation plants, chemical and oil refineries, etc. and making them energy efficient for sustainable development. The present work dealt with this aspect wherein the unused energy of the hot water transportation pipelines, which was earlier throttled by pressure differential control valve (PDCV), was harvested and used elsewhere. A special class of multi-purpose micro hydro turbine known as the positive displacement turbine was developed for the present application which involved very low flow rates with high heads and very low specific speeds and to replace the PDCV which was frequently failing due to cavitation causing loss of energy. A framework was developed for designing such turbines and predicting their performance using CFD. The reasons for the occurrence of cavitation and flow pulsations were also examined and remedial measures were incorporated for their elimination. At the rated condition during experimental study, the base design generated 7.31 kW power with an overall efficiency of 67.7%. The socio-economic analysis was also carried out which concluded that the PDT will aid in energy conservation and reduction in CO2 emissions. •Description of Pressure Differential Control Valve (PDCV) replacement by Positive Displacement Turbine (PDT).•Develop framework for design & performance prediction of special class of multi-purpose PDT.•Demonstrate PDT’s application in energy recovery for high head & very low flowrate conditions.•Recover unused energy from the hot water supply pipelines and make it energy efficient.•Brief description of socio-economic impact associated with the use of PDT.