Bacterial 16S rRNA gene amplicons were sequenced using the Illumina MiSeq platform to investigate DNA samples from three drinking water distribution networks in Norway (Bergen, Stavanger, and Trondheim). Samples included raw source water, finished drinking water product (effluent from the water treatment plant), hot and cold tap water from the distribution network, biofilms scraped from the surfaces of water mains, and communities from under corrosion scale and tubercles on the walls of unlined cast-iron water mains.