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KI-Symbolbild: Techniker von hinten gesehen an einem großen Warmwasserspeicher mit Rohrleitungen in einem hellen Technikraum.
Advice Letting Germany

A Legionella finding reaches the action value: organise the operator process from the laboratory report immediately

An elevated Legionella finding triggers a separate operator process. Keep the health authority, cause investigation, risk assessment, measures and consumer information together with documented status.

Automatically translated – the German version is legally binding. Show original (German)

Published
19 Oct 2026
Research as of
17 Oct 2026
Applies to
Germany
For whom
Owners & landlords
Article ID
WX26-P03-0107

A laboratory report is available for the rented building. The responsible specialised party confirms that the technical action value for Legionella spec. has been reached. If you carry operator responsibilities for the affected water supply system, this finding now requires its own immediate processing procedure. Filing it away until the next routine inspection is not sufficient.

Bring the finding and the responsibility together immediately

Secure the complete report with attachments, sampling locations and receipt. Clarify without delay the concrete operator responsibility as well as the appropriate specialist support and the contact to the competent health authority. This article does not provide its own laboratory assessment and does not establish a general duty to investigate.

§ 51 TrinkwV already links its duties to act to the reaching of the technical action value. The operator must inform the health authority without delay, insofar as they do not have proof of the notification already made by the accredited testing laboratory. § 53 regulates the laboratory’s own duty to notify. [BETREIBER, LABOR]

Therefore ask for the actual proof of notification. The presumption that the laboratory will take care of it will not be accepted as proof of notification. At the same time, the further operator tasks are organised independently of who transmitted the notification.

Relate the specialist assignment to the results required by law

§ 51 requires determination of the cause including an on‑site inspection and review of the generally accepted rules of technology, a written risk assessment and the necessary protective measures. The recommendations named in the standard must be observed. [BETREIBER]

Our editorial recommendation: hand over the report, the system schematic and known changes together. Have it confirmed who will process which investigation and which written result. The technically authoritative version of the included recommendations is clarified in the assignment. The letting does not replace this process by its own temperature settings, flushing plans or a self‑devised disinfection.

Carry consumer information and possible orders

Under § 52 paragraph 3, affected consumers must be informed without delay after the operator has received the result of the risk assessment as well as usage restrictions and other recommendations addressed to them. In addition, and in particular in the case of official orders for hazard prevention, further information duties exist. Under its conditions § 68 also enables the health authority to issue immediate information or other protective orders. [INFORMATION, AMT]

Therefore coordinate the necessary current communication and its recipients with the specialised party and the health authority. A still outstanding written result is not a release by you for the previous use. Notices are passed on with their actual content and updated appropriately if the status changes.

Fictitious case: The notification has been made, the process remains open

An operator receives proof that the laboratory has notified the health authority. In her initial task list this means only that the notification is done. She adds the other actually required work steps: determination of the cause, written risk assessment, coordinated protective measures and affected consumer information.

Each step is given responsibility, current status and next necessary contact. A confirmed appointment for the inspection is not described as an already available risk assessment. This way it remains visible what still needs to be decided and implemented by specialists.

Document measures and completion in a traceable way

§ 51 obliges to the immediate communication of measures taken to the health authority and to the submission of the risk assessment on request. Completed measures must be documented immediately; the documentation must then be available for ten years. [BETREIBER]

Therefore record the course up to the further steps clarified technically and by the authorities. A contracted company and a sent message are important intermediate statuses, but they do not replace the results that are still outstanding. Health issues, concrete usage restrictions and technical remediation remain within the specialist process responsible for them.

Sources and context

Created with the help of AI and editorially reviewed. General guidance only; not individual legal, tax or financial advice. Errors and later changes are possible.