“The distribution system is the remaining component of public water supplies yet to be adequately addressed in national efforts to eradicate waterborne disease” (NRC, 2010). Current disinfectant residual guideline values in Canada and the US have not been established using scientific evidence for the protection of the public from specific pathogens or health outcomes such as acute gastrointestinal or respiratory illnesses. Our current research in the drinking water distribution system seeks to inform this issue by investigating the role disinfectant plays in a full-scale distribution system and what current levels of disinfectant are doing microbial water quality in North American drinking distribution system. This work will help inform National and International discussions regarding the level of chemical disinfectant residual is necessary to best protect the public from acute gastrointestinal illnesses (AGI) and respiratory illnesses. As water infrastructure ages in our cities, we need more research to understand what management strategies are needed to protect public health.