 There is heated debate in the United States about the extent to which waterborne infectious diseases may be transmitted to human beings through drinking water that meets federal standards for pathogen removal. This debate is even more pronounced among elderly immunocompromised persons and their health care providers because of the prolonged illness syndromes generally gastrointestinal and even death that may occur in these persons after the ingestion of infectious agents. Concerns about drinking water have been heightened by the findings of Payment et. al. in Canada which suggested that approximately 25 of highly credible gastrointestinal illness in a community might be due to drinking water. 