Since scale in water supplying pipes is one of the major sources of water contamination and user’s complaint, detection of scale is very important for the proper maintenance of water piping. In the present study, the potential of guided waves was explored for the detection of scale in water supplying pipes. Using variable angle wedges, several modes of guided waves were generated and identified. In the experiments, it were observed that the amplitude of F(M,2) (M=1,2,3,4) modes decreased significantly as the increase of the amount of scale. The result of the present study recommended that the F(M,2) modes are optimal to detect scale in water supplying pipes. © 2003 American Institute of Physics