<qa>  What is the primary objective of this study?The principal objective of this study is to evaluate the ability of in-home treatment of tapwater to reduce gastrointestinal illness in non-institutionalized elderly individuals. The trial will test household-level treatment of drinking water by joint use of ultraviolet light and filtration devices. A secondary objective is an estimate of the incidence of specific bacterial, viral, and protozoan agents in stool specimens collected from elderly individuals with gastrointestinal symptoms that might be related to water consumption. 