DIN CEN/TR 16355:2012-09

Legionella are small (up to 6 micrometres in length) rod-shaped bacteria. They are aerobic and can be detected in all moist environmental compartments, such as soil, surface waters, groundwater and in concentrations not considered infection-relevant. In addition to Legionella pneumophila, which is the most significant type in terms of epidemiology and drinking water hygiene, more than 50 other types are known. In contrast to other pathogenic bacteria they do not reproduce in the human body, but under suitable conditions, for example, in biofilms in the temperature range from 25 °C to 50 °C. The following incident is responsible for the designation of these particular bacteria: 220 out of more than 4 000 participants fell ill during a congress of the American Legion in Philadelphia/USA in 1976; this resulted in 30 fatalities. It took a few weeks to classify this special type of pneumonia ("Legionnaire's disease") as an epidemic. An increased risk of this type of pneumonia (legionellosis) shall be assumed when critical concentrations are reached, long-term standing water (stagnation) under the aforementioned temperature conditions in parts of drinking water installations (pipelines and tanks, among others) being the most significant cause. In the meantime, the connection between contamination of drinking water installations and the risk of infection for users has also been substantiated by a number of corresponding analyses and proof in Germany. This Technical Report provides essential information about the conditions for Legionella growth in drinking water installations (according to the DIN EN 806 series and DIN 1988) up to the tapping points and recommendations to inhibit Legionella growth in these installations. This Report considers maintaining the temperature outside of the aforementioned range within which Legionella growth can take place as one possibility of the technical concept for inhibiting the reproduction of Legionella in these drinking water installations, as well as carrying out precautions for thermal disinfection as the most frequently utilized and most proven measure. The current status of this document was selected due to the fact that the largest part of its content does not completely coincide with previous practice and legal provisions in the member states. This Report provides recommendations for good practice concerning prevention of Legionella growth in drinking water installations, although the local national regulations still remain in force. This Technical Report has been prepared by CEN/TC 164/WG 2 "Internal systems and components" (secretariat: DIN). The responsible German standardization committee is Technical Committee NA 119-04-07 AA "Häusliche Wasserversorgung" ("Domestic water supply") at the Water Practice Standards Committee (NAW).