Potable water supply systems harbor diverse microorganisms that humans are exposed to through drinking, inhalation, and skin contact. Various factors in water production and distribution have been shown to shape the microbial communities in city tap water, however, the effects of water supply pipes in buildings have not been directly tested.
Here we examine the tap water bacterial community change in buildings where water use was strictly controlled, and show that community compositions drastically different from fresh city tap assembled in building water supplies when water use was paused and examine the community assembly processes.
When modelled under a neutral community assembly framework as islands connected to two mainlands – city tap water and distribution system biofilms, the stagnant water communities from proximal to distal pipes are shown to move from under the influence from the water-mainland to the biofilm-mainland. Our results suggest that the physical structure of water supplies dictates the community assembly in building water supplies in predictable processes, enable design of water microbiome.