A new online course on water use modeling has been developed by Gauge to respond to increasing pressure to understand and reduce water use in buildings. It includes a simple water modeling tool in Excel, the Water Use Modeling (WUM), which can be populated with information from an existing building or a proposed building design to produce reports of predicted water use in relation to targets. The tool is a very effective way of understanding water use in buildings and developing strategies to reduce this through practical measures. The course is not highly technical and is suitable for anyone wishing to understand water uses in buildings and how this can be reduced.