Abstarct:   In addition to reducing water leakage, PATs in WDNs use the excess pressure to produce renewable energy. In the first part of the present research, due to the importance of environmental issues caused by the emission of GHGs and mentioning that in the existing optimization objective functions, only water and energy aspects have been addressed, a new objective function with a water-energy-environment approach is presented. The optimization results of the new objective function (number, settings, direction, and location) on the two WDNs known as 25-nodes (Case1) and the Damavand city (Case2) show 40 and 45% leakage reduction, respectively. Adding the social cost parameter of carbon dioxide to the energy tariff in the new objective function caused the investment period payback for the three optimized PATs in Case1 to be calculated about 45.2 months. Also, according to the electricity produced by three optimized PATs in Case2, the installation of this equipment will supply the electricity needs of about 255 households (Iran). In the second part of the research, due to the weakness of existing reliability indices in determining the reliability of networks equipped with PATs from the energy aspect (when component failure scenarios occur) for the first time a new reliability index called ERI will be introduced. Then to investigate the performance of networks from the water and energy aspect, the new index will combine with some existing hydraulic reliability indices. The results of the performance analysis of Case1 in terms of energy (under all simultaneous multi-pipe failure scenarios) introduce pipes No. 2 and 36 as the most critical pipes for repair and maintenance. Similarly, by analyzing the performance of Case3 (the network connected to the reservoir No. 23 in Tehran) in all aspects of energy, water adequacy, and water equity (under one pipe failure scenarios), pipes No. 2, 4, 31, and 55 were determined as the most critical pipes. The energy loss due to the worst failure scenario showed that the simultaneous failure of pipes 2-12-21 in Case1 and pipes 2-4 in Case3 can be caused the energy loss produced by PATs completely.