In order to meet regulatory requirements and customer expectations, water utilities are feeling a growing need to understand better the movement and transformation undergone by treated water introduced into their distribution systems. Computerized simulation models are becoming popular and essential tools for tracking the fate of water and its quality transformations within distribution systems. EPANET represents a third generation of public domain software developed by the US Environmental Protection Agency's (EPA's) Risk Reduction Engineering Laboratory for modeling water quality within distribution systems. The program performs extended period simulation of hydraulic and water quality conditions within pressurized pipe networks. It tracks the flow of water in each pipe, the pressure at each pipe junction, the height of water in each tank, and the concentration of a dissolved substance at each junction during a multi-time period simulation. In addition to concentration, water age and source tracing can also be simulated.