Legionella examination; notification of exceeding the technical measure value

Drinking water must be regularly tested for legionella. Not only public facilities are affected, but also landlords under certain conditions.


According to the Drinking Water Ordinance, the entrepreneur and the other owner of a drinking water installation (permanent water distribution) must have the water tested for legionella at several representative sampling points if

  • it contains a large-scale system for heating drinking water
  • and showers or other aerosol-generating devices (e.g. whirlpool baths) are present in it,
  • and if drinking water is dispensed from it as part of a commercial and/or public activity.

In the case of leasing, house owners, landlords or owners' associations (represented by a property management company, if applicable) are considered to be entrepreneurs and other proprietors.

Large systems for heating drinking water are systems with a storage water heater or a central flow water heater - each with a capacity of more than 400 liters or more than 3 liters in at least one pipe between the outlet of the drinking water heater and the tapping point. The content of a circulation pipe is not taken into account. Corresponding systems in one- and two-family houses do not count as large systems for heating drinking water.

In the case of rental, the inspection must be carried out at least once every three years, and in the case of drinking water provision as part of a public activity, the inspection must be carried out at least once a year. If no complaints have been found during the annual inspections in three consecutive years, the health authority can also specify longer inspection intervals of up to three years, provided that the system and mode of operation have

  • have not been changed and
  • demonstrably comply with the generally recognized rules of technology.

The examinations must be carried out in accordance with § 14b TrinkwV (Drinking Water Ordinance) and without being initiated by the health authority. The examination intervals according to § 14b Abs. 4 TrinkwV apply:

  • Installations (public activity): at least annually
  • Plants (commercial activity): at least every 3 years,
  • Mobile supply systems, e.g. on board land, water and air vehicles: the health authority determines the frequency.

For newly commissioned drinking water installations, the first examination in accordance with § 14b para. 6 TrinkwV must be carried out within three to twelve months after commissioning.

For contamination with Legionella, a so-called technical action value (TMW, value for triggering measures) of 100 CFU (colony-forming units) per 100 ml applies. In the case of examinations according to § 14b para. 1, the examination body must immediately notify the responsible health authority if the TMW is exceeded in accordance with § 15a TrinkwV. In addition, the entrepreneur and other owner of the facility (owner, property management) bears primary responsibility for the measures required under the Drinking Water Ordinance if the TMW is exceeded:

  • The entrepreneur or other owner must immediately notify the health office of the exceedance in accordance with Section 16 (1) of the Drinking Water Ordinance, if this has not already been done by the testing agency.
  • According to § 16 para. 7 TrinkwV, the entrepreneur or other owner must immediately carry out or have carried out investigations to clarify the causes, including a site inspection as well as an examination of compliance with the generally recognized rules of technology. In addition, he must prepare or have prepared a hazard analysis and take measures necessary to protect the health of consumers. The health authority must be informed of the measures taken.
  • The entrepreneur or other owner must inform the affected consumers immediately about the result of the hazard analysis and any resulting restrictions on the use of the drinking water.

In principle, the entrepreneur and the other owner of the drinking water installation must inform the affected consumers about the result of the legionella analysis in an appropriate and up-to-date manner. Upon request, individual results must be made available to the affected consumers (§ 21 para. 1b TrinkwV).

In the event of extremely high legionella levels (over 10,000 CFU/100 ml), the showers may no longer be used until the problem has been eliminated. Use of the showers during this period is only possible if terminal bacteria-proof filters are installed.

Required documents

  • detailed laboratory findings need only be submitted on request


Responsible for editing:Bayerisches Staatsministerium für Gesundheit und Pflege

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