If pipes are damaged in a water distribution network (WDN), adjacent valves are closed to isolate the pipes for repair. Due to the closed valves, parts of WDN are isolated from water supply sources. The isolated area is divided into Intended Isolation Area (IIA) and Unintended Isolation Area (UIA). The IIA occurs by intention to isolate the damaged pipe, while UIA is unintentionally disconnected from the sources due to IIA. Thus, the extension of isolated area and suspended flows are mainly affected by number and location of installed valves in WDN. In this study, optimization models were developed to determine optimal valve locations in WDN. In a single-objective model, total water supply suspension is minimized, while a multi-objective model intends to simultaneously minimize the suspended flow and valve installation cost. Optimal valve placement results obtained from both models were compared and analyzed using a sample application network.