Organisms that become established in water supply may also be opportunistic pathogens. Representative opportunistic pathogens that are waterborne include acid-fast bacteria, fecal klebsiellae, Legionella and Pseudomonas aerugionosa. These organisms may be found in the heterotrophic bacterial population of treated drinking water and if appropriate conditions exist, may colonize and become part of the biofilm. Maintaining a high quality water supply requires careful treatment and a clean water distribution system. Users of the community water supply also have a responsibility to preserve the water quality from deterioration as it leaves the service meter and traverses the building supply lines. The goal is to minimize exposure to various heterotrophic bacteria that may pose a risk to those consumers of varying health status in the community of people.