Water-main biofilms, tap water, and corrosion-associated communities were collected from a chloraminated drinking water distribution system (DWDS) in the United States and a DWDS in Norway that does not maintain a residual disinfectant. Bacterial 16S rRNA genes were sequenced with paired-end Illumina MiSeq to provide taxonomic and ecological information from the samples. There is interest in characterizing the organisms throughout full-scale DWDSs to identify dominant taxa as well as potential nuisance organisms (e.g., waterborne pathogens, organisms associated with microbiologically influenced corrosion of water mains). Additionally, by comparing different DWDSs, it may be possible to infer relationships between operation or water quality and the microbiome.