Local high points widely exist in wastewater pressure pipe system. In reality, wastewater pumps are cyclically switched on and off so that the force mains may not be always pressurized as usually assumed. Understanding the hydraulics of those gravity driven pipes is very important to the reliable operation of wastewater pumping. In this study, a differentiation-based method was developed to determine the temporal and spatial dynamics of wastewater in force main by solving the equations involving pump curves and system curves for both gravity-driven and pressurized flows. The solutions to the equations determine the operation points of pumps. The method was applied to a wastewater pumping system of the City of Lakeland, Florida, with multiple local high and low points in the force main. Field investigations and theoretical analyses are incorporated to calibrate pump head characteristic curve and pipe friction coefficient, enabling more accurate simulation of force main hydraulics. With its simplicity and affordability, this method would be of interest to water utility engineers. (C) 2017 American Society of Civil Engineers.