Legionella

Legionella are gram-nega­tive, aerobic bacteria that occur natu­rally in small numbers in non-salt surface waters and soil. Under certain condi­tions, Legionella can multiply in water-carrying pipes and fixtures. The optimal temper­a­tures for this are between 25°C and 45°C.

Legionella are clas­si­fied as poten­tially path­o­genic to humans; inhala­tion or microaspi­ra­tion of water droplets containing Legionella can cause Legion­naires’ disease, a form of pneu­monia, or Pontiac fever in humans.

According to the currently valid German drinking water regu­la­tion (TrinkwV), busi­ness owners and other oper­a­tors of a water supply system are required to have the drinking water tested for Legionella as part of a systemic exam­i­na­tion in build­ings if the drinking water is dispensed as part of a commer­cial or public activity, if a large drinking water heating system is present, and if the water supply system contains showers or other facil­i­ties that result in the atom­iza­tion of the drinking water.

A large drinking water heating system is present if the drinking water heater has a storage volume of more than 400 liters or if there is a pipeline with a capacity of more than 3 liters between the outlet of the drinking water heater and the point of withdrawal.

Note: Oblig­a­tions for Legionella testing may also arise from other legal areas besides the German drinking water regulation.

If the drinking water is supplied as part of a public activity, the systemic tests for legionella must be carried out annually

The health depart­ment can extend the interval up to three years under certain conditions.

If the drinking water is supplied as part of a commer­cial activity, but not a public activity, the systemic exam­i­na­tions for legionella must be carried out at least every three years.

If one of the above-mentioned systems is put into oper­a­tion for the first time, a legionella exam­i­na­tion must be carried out within 3 – 12 months after commis­sioning in accor­dance with § 14b para. 6 TrinkwV [1].

According to the currently valid Drinking Water Ordi­nance [1], samples must be taken at several repre­sen­ta­tive and suit­able sampling points as part of a systemic legionella exam­i­na­tion in accor­dance with the recom­men­da­tion of the Federal Envi­ron­ment Agency dated December 18, 2018 [2]. Samples are to be taken at the drinking water inlet and outlet of the drinking water heater as well as in the periphery to detect each riser.

If the tech­nical action value of 100 CFU per 100 milli­liters is exceeded in the course of a systemic exam­i­na­tion for Legionella, the labo­ra­tory is oblig­ated according to the currently valid Drinking Water Ordi­nance [1] to inform the respon­sible oper­ator as well as the respon­sible health authority.

Drinking water samples must be taken as part of an analysis for legionella in accor­dance with the Drinking Water Ordi­nance [1] by testing labo­ra­to­ries accred­ited for this purpose and approved in accor­dance with § 15 Para.4 Drinking Water Ordi­nance [1].

[1] Trinkwasserverord­nung in der Fassung der Bekan­nt­machung vom 10. März 2016 (BGBl. I S. 459), die zuletzt durch Artikel 1 der Verord­nung vom 22. September 2021 (BGBl. I S. 4343) geän­dert worden ist.

[2] Systemische Unter­suchungen von Trinkwasser-Instal­la­tionen auf Legionellen nach Trinkwasserverord­nung – Probe­nahme, Unter­suchungs­gang und Angabe des Ergeb­nisses. Empfehlung des Umwelt­bun­de­samtes vom 18. Dezember 2018

[3] Trinkwasser­erwär­mungs- und Trinkwasser­leitungsan­lagen – Tech­nische Maßnahmen zur Vermin­derung des Legionel­lenwach­s­tums – Planung, Errich­tung, Betrieb und Sanierung von Trinkwasser-Instal­la­tionen, DVGW-Arbeits­blatt W 551, Berlin: Beuth-Verlag, April 2004