[Practical and legal aspects on the presence of Legionella in drinking water installations].

A drinking water installation is often only a small component of building engineering systems and in general practice it is rarely the focus of the work of local personnel. There are not only the specifications of manufacturers, but also numerous "generally accepted rules of technology" must be complied with when operating these building engineering systems. The foremost ones pertinent to this topic are discussed in this article. However, noncompliance with the "generally accepted rules of technology" can cause contamination with Legionella, and the actions that would then need to be taken must be based on each specific case. The prerequisite for permanently eliminating any contamination with Legionella is identifying the precise causes and basing all ensuing action on that. Correctly transforming the existing "generally accepted rules of technology" into reality would be a sufficient guarantee to reach a target of less than 100 cfu/100 ml for Legionella. This article illustrates that this target can be reached by renovation and without applying any disinfectant processes even in drinking water installations with an extremely high level of contamination. Furthermore, this article presents examples of the legal aspects of the topic of Legionella from the point of view of the engineer. Finally, the trend toward operating drinking water installations at a lower temperature to save energy while applying disinfection is viewed critically by the authors.