Legionella

According to the Drinking Water Ordinance, the operator or owner of a large-scale hot water system is obliged to have the water regularly tested for legionella. An approved laboratory must be commissioned for this purpose.

An obligation to test exists if the following points are fulfilled:

• Drinking water is supplied from the water supply system as part of a public activity (e.g. schools, daycare centers, etc.) or commercial activity (e.g. rentals).
• A large-scale system is present - with more than 400 liters of storage volume and/or more than 3 liters of pipe content. These are primarily systems with central drinking water heaters.
• The water supply system contains showers or other facilities where water misting occurs.

If the technical action value for legionella is exceeded in the water supply systems, then special notification and action obligations apply.

The operator must:

• Report exceedances to the public health department.
• Carry out investigations to clarify the causes. These investigations include, among other things, a site inspection. The drinking water installation must be checked for compliance with the technical specifications.
• prepare a hazard analysis.
• carry out the measures required by the generally recognized rules of technology to protect the health of consumers.

All affected consumers must be informed immediately of the result of the hazard analysis and any resulting restrictions on the use of the drinking water.

Detailed information on the operator's duty to act in the event of exceedances of the technical measure value for legionella as well as the feedback form to be filled in and submitted to the public health department can be found under "Further information".