The paper presents the process of computer modeling to reconstruct the actual working conditions of the water supply network in Mońki, Białystok county. The calculations made it possible to simulate the operation of the network and make decisions affecting the efficiency of the entire system. The computer program EPANET 2.0 was used, which was created by the U.S. Environmental Protection Agency (EPA). It allows for periodic hydraulic simulations and provides an image of water operation in the pressure pipeline network. The study included the model of the evaluated network in terms of basic quality parameters such as flow velocity, pressure, unit losses, water age and operating conditions during simulated network failure.