In recent years, the water supply industry and general public have become increasingly interested in the quality of water in distribution systems. Correspondingly, the U.S. Environmental Protection Agency (USEPA) has been developing standards that focus attention on the quality of the water at the customer's tap, in addition to their historical standards that emphasize the quality of water leaving water treatment plants. In particular, the Stage 2 Disinfection Byproducts Rule (DBPR) will require water purveyors to focus on water quality at all points in the distribution system. This paper discusses guidance related to Stage 2 Initial Distribution System Evaluation (IDSE) compliance, and use of distribution system modeling for overall water quality management and assistance with regulatory compliance. The paper discusses the methodology and theory behind developing a sophisticated system model, and includes discussion of two recent projects in which this type of model was used for the utilities' IDSE report and subsequently for system operational adjustments. The Charleston Water System, South Carolina, and Town of Cary, North Carolina, both found value in using their previous investment in developing a hydraulic models, which were refined using intensive time-of-travel calibration to exceed the requirements of the IDSE. The models can be subsequently used to implement system operating protocols to refine water quality. These operating practices include system tank fill/drain operations, efficiency of system pumping operations, flushing programs, emergency response, and response to other system water quality issues. Includes tables, figures.