This presentation details some OpenSource tools dedicated to water network management, be it for water distribution or wastewater networks. The qWAT project is a specific tool based on QGIS and PostGIS. it aims at managing water distribution networks. The data model is part of the project and covers most use cases for this kind of assets. The qWAT project is strongly linked to QGIS, and tries to contribute to the core of QGIS so as to mutualize developments and features among other QGIS-based applications. Similarly, the QGEP project is dedicated to wastewater networks. We also present a use case for an implementation of a wastewater information system in France, based on QGIS and PostGIS. Furthermore, we show how PostGIS-based projects allow to do network and graph analysis, so as to extract meaningful information for decision-taking and planning. QGIS-Epanet and QGIS-SWMM are two QGIS Processing extensions integrating simulation features on water distribution and wastewater networks. They let the user run simulations to analyze the network, dimensioning, and identify specific issues. These set of tools show that OpenSource GIS now tend to fulfill use cases for specific fields of application, and water management is among them.