Leaks are present to some extent in all water-distribution systems. This paper proposes a leakage localisation method based on the pressure measurements and pressure sensitivity analysis of nodes in a water distribution network. The sensitivity analysis using analytical tools is not a trivial job in a real network because of the huge non-explicit, non-linear systems of equations that describe its dynamics. Simulations of the network in presence and absence of leakage may provide an approximation of this sensitivity. A fault isolation algorithm which correlates on line the residuals (generated by comparing the available pressure measurements with their estimation using a model) with the fault sensitivity matrix is used. The proposed algorithm has been applied in simulation to a DMA (District Metered Area) in the Barcelona Network using EPANET software. The results obtained were promising