A method and system for assessing the condition of a pipe carrying a fluid is disclosed. The method includes the steps of generating a pressure wave in the fluid being carried along the pipe and detecting a pressure wave interaction signal resulting from an interaction of the pressure wave with a localized variation in pipe condition. The method then involves determining from the timing of the pressure wave interaction signal the location of the localized variation in pipe condition and the extent of the localized variation in pipe condition based on a characteristic of the pressure wave interaction signal.