In the present work on-line computational techniques have been developed and used in the analysis of hydraulic transients caused by leakage, in order to detect and locate pipeline ruptures. Pressure transients were obtained in two PVC pipelines 3/4" diameter by using four pressure transducers connected to a PC computer equipped with A/D and DIA converters. The pipelines were 433 m and 1,248 m long. Leaks were simulated at different positions along the pipelines. Experiments were carried out for different liquid flow rates corresponding to Reynolds number in the range from 2,000 to 13,000. Leak percentage were in the range from 5% to 50% of the nominal liquid flow. A computer program to be run on-line was developed to simulate the leak, to read and filter the pressure transducers data, to display the pressure transient plots and to obtain leak location information. The detection system showed good performance in the detection of small leaks. Leaks as small as 5% of the nominal liquid flow rate are readily detected. Leak locations were computed from pulse time delay between the various pressure transducers. The computed leak positions approached the actual values with precision. The developed software shows to be a very useful tool to the automatic supervision of pipelines as instantaneous leaks are readily detected and located.