The causes of water quality problems in distribution systems are difficult to identify because they can be related to numerous sources. A tool has been developed to integrate and analyse water distribution system data with the help of geographical information system (GIS) technologies. This approach uses a flexible software architecture to gather data on distribution system structural elements, water quality sampling and especially distribution system events, all of which can be key to explaining water quality problems. The tool has been applied to five water utilities in North America and Europe, all with different data formats and data gathering practices. The approach was successful in explaining about 40% of positive coliform samples at the Laval (Quebec) utility. It also led to better data quality and responsiveness at the utilities.