For most communities, potable source waters are treated within public utilities to ensure acceptable water quality prior to delivery to the consumer. This chapter describes the typical water treatment trains that are typically utilized including: filtration; coagulation; flocculation; sedimentation; and chlorination. However, despite treatment, potable waters are not sterile and still contain microorganisms, particularly bacteria. Here we describe potential microbial growth that can occur within water as it is transported to consumers within water distribution systems. In addition, microorganisms can be introduced into potable waters via intrusion events that can occur due to pipe breakages. Thus, the chapter concludes with a discussion of real and near real time technologies that can be used to monitor potential microbial contaminants in water distribution systems.