Complex building premises plumbing systems provide an ideal niche for diverse waterborne microorganisms, including opportunistic pathogens such as Legionella pneumophila. In this field study, we collected cold and hot water samples from premises plumbing systems of nine different high-rise buildings and examined the L. pneumophila culturable positivity and concentration to examine microbial ecology trends associated with L. pneumophila colonization. In addition, bacterial community structure was evaluated using high throughput 16S rRNA gene sequencing. 9.1% (2/22) of cold-water samples and 30.5% (18/59) of hot water samples were positive for L. pneumophila culture. 16S rRNA gene sequencing demonstrated a diverse bacterial community in the sampled premises plumbing systems. The phyla Proteobacteria, Acidobacteria, Bacteroidetes, Gemmatimonadetes, Planctomycetes, and Thermi represented a combined 97.7% average relative abundance, dominating the bacterial community. Also, an apparent bacterial community difference was observed between cold water and hot water. Interestingly, by examining cold water and hot water separately, we identified several bacterial taxa in the phyla Bacteroidetes, Gemmatimonadetes, and Acidobacteria were significantly enriched in L. pneumophila culture positive samples, while taxa in Proteobacteria were significantly enriched in L. pneumophila culture negative water samples. The correlation of L. pneumophila colonization and bacterial community structure suggests a potential association between this waterborne opportunistic pathogen and the premises plumbing microbial community, which merits further research.