In water distribution systems (WDSs), operational modeling results could be affected by accuracy of pipe friction parameters (PFPs). Under a single hydraulic condition, unique values of PFPs cannot be achieved, even with the availability of pressure and discharge values at every node. This study established a theoretical model of PFP identification in WDSs by decoupling variables. Then, equations for identifying PFPs were expressed through energy conservation equations of a tree and relationships between pressure losses and flows in pipes under different hydraulic conditions. Further, equations for identifying PFPs can be transformed into linear simultaneous equations by substituting variables whose solvability is easy to study. The aim of this study is to develop a theoretical framework for identifying unique values of PFPs and provide a theoretical basis for an actual problem of PFP identification in a WDS. Moreover, a theoretical demonstrative example is presented to illustrate processes of obtaining unique and acceptable values of PFPs.
