The purpose of this paper is to show the possibilities offered by Scilab/Xcos to model hydraulic time-dependent systems. In particular, we develop a new Xcos module combined with the use of Modelica language to show how water distribution systems can be modeled and studied. In this paper we construct a reduced library composed by few elements: reservoirs, pipes and nodes. The library can be easily extended to obtain a more complete toolbox. The developed library is tested on a simple well-known hydraulic circuit.