Biofilms invariably colonize drinking water distribution systems with intensities and patterns governed by the habitat's environment. Water temperature and flow dynamics, nutrient availability, disinfectant residual and pipe material determine their development, structure and composition. Drinking water pipe biofilms control microbial regrowth and are a possible source of pathogens. However, these are possibly released at levels that do not generally impart hazards to healthy drinking water consumers. A deeper understanding of drinking water biofilms microbial ecology must be achieved before this issue can be adequately assessed.