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Drinking water testing for Legionella

Gesundheitsamt (public health office) · Environmental hygiene

Two testing cyclesObligation for landlordsAccredited laboratory

The testing obligation is set out in the Drinking Water Ordinance (Trinkwasserverordnung, TrinkwV), § 31 TrinkwV, and it recognises two intervals, not one. Where drinking water is supplied as part of a commercial activity — the normal case for renting and leasing — it must be tested at least every three years. Where it is supplied as part of a public activity — hospitals, care homes, schools, hotels, sports facilities — it must be tested at least once a year; the Gesundheitsamt may extend this interval to three years under certain conditions. Only installations that meet all three criteria are affected: a storage water heater holding more than 400 litres or more than three litres of content in a pipe between the heater and the outlet, a shower or another fitting that atomises water, and the building is not a one- or two-family house.

The figure of 100 per 100 millilitres is correct, but its usual name is not: Annex 3 Part II TrinkwV lists Legionella spec. as a technical action level, not as a limit value. The difference is practical, not merely linguistic. Water that exceeds a limit value becomes legally unusable; an exceeded action level triggers a procedure — notification to the Gesundheitsamt, hazard analysis, measures, re-testing. The water is therefore not automatically shut off, and the authority decides what to do according to the level of the findings. Anyone who treats the figure as a prohibition threshold reacts either in a panic or not at all — both wrong.

Not every laboratory may carry out the test itself: what is required is an accredited laboratory authorised for drinking water testing, and sampling takes place at the prescribed points — the heater outlet, the circulation return and representative sampling points on the risers. A result from a DIY-store test kit does not fulfil the obligation, even if it states the same figure.

The party liable for the test is the operator of the water supply installation — in rented buildings, therefore, the owner, not the tenant. The costs, however, form part of the service charges and may be passed on to tenants; this follows not from the TrinkwV but from tenancy law — the TrinkwV regulates the obligation, not its allocation.

Last updated28 August 2026
Legal basis§ 31 TrinkwV
VerificationChecked against IfSG, TrinkwV, LFGB and Regulation (EC) 852/2004
Written and reviewed byAndrés Sánchez Botta
Independent information website: we are not the Gesundheitsamt, not an authority and not a paid advice service – we do not submit applications on your behalf. All information comes from official sources and is explained here in plain language; binding information always comes from the competent body. No legal advice and not an official authority. We are neither lawyers nor tax consultants: we document official procedures and check the information against the official source – this is information, not legal or tax advice.
CommercialEvery three years§ 31 TrinkwV
PublicAnnuallyExtension possible
Action level100/100 mlNot a limit value
Maximum regulatory fineUp to €25,000§ 73 IfSG via § 72 TrinkwV
Required documents

What you need

The installation’s data

The capacity of the storage water heater, the pipe volume between the heater and the outlet, the number of risers and residential units. This determines whether the obligation exists at all: a storage capacity of more than 400 litres or more than three litres in the pipe, plus a shower or other atomising fitting.

Proof of the laboratory’s accreditation

Only a laboratory that is accredited and authorised for drinking water testing may carry out the examination. Ask for the authorisation to be stated before you place the order — a result from an unauthorised source does not fulfil the obligation.

The sampling plan

Where samples are taken is prescribed, not arbitrary: the heater outlet, the circulation return and representative sampling points. The plan forms part of the result and is part of the proof provided to the Gesundheitsamt.

Previous years’ results

They show trends and, in case of doubt, justify an extension of the testing interval for public activity. Without previous results, the authority decides solely on the basis of the current situation.

If the level is exceeded: the hazard analysis

It is not prepared by the laboratory but by a qualified person, and it is the real core of the obligation following an abnormal result. Its outcome determines the measures and the re-test.

Step by step

How to proceed

  1. 1

    Check whether the installation is covered at all

    Three criteria must be met together: a storage capacity of more than 400 litres or more than three litres of pipe content, a shower or other atomising fitting, and the building is not a one- or two-family house. If one is missing, the obligation does not exist.

  2. 2

    Determine the correct interval

    Commercial supply — the normal case for renting and leasing — every three years. Public supply, for example in a clinic, care home, school, hotel or sports facility, once a year. Anyone who chooses the wrong interval misses the deadline by up to two years.

  3. 3

    Commission an authorised laboratory

    Check the accreditation and the authorisation for drinking water, and arrange sampling by trained personnel at the prescribed points. Prices are market prices, not fees — it is worth comparing quotes.

  4. 4

    Assess the result

    Below the action level: document the result and note the date of the next test. Above it: inform the Gesundheitsamt without delay, arrange a hazard analysis, implement measures and re-test. The level is a trigger, not a shutdown.

  5. 5

    Do not overlook the ancillary obligations

    Affected consumers must be informed; for lead pipes, § 17 TrinkwV additionally applies, with the deadline of 12 January 2026, the possibility of an extension and the written confirmation required from 13 January 2026.

Fee information

Costs and payment

Costs, deadlines and scopeLaboratory costs are market prices, not fees
ExaminationLaboratory’s market price
Commercial intervalEvery three years
Public intervalAnnually
Action level100 per 100 ml
Lead pipesDeadline 12 January 2026
Maximum regulatory fineUp to €25,000

The TrinkwV does not set out its own regulatory fine amounts: its § 72 declares infringements to be a regulatory offence within the meaning of § 73 of the Protection against Infection Act (Infektionsschutzgesetz, IfSG), which sets out the framework. Where there is a danger to health, the criminal offence under § 71 TrinkwV may additionally apply.

Good to know

Important notes

A shortened version of the lead ban is in circulation. The correct position is: § 17 TrinkwV requires lead drinking water pipes to be removed or decommissioned by the end of 12 January 2026. The statement “since 12 January 2026 all lead pipes must be out” is incomplete, because the provision allows for extensions — among other things for private installations until 12 January 2036, where there is no danger to human health. In addition, there is an obligation that hardly anyone mentions: from 13 January 2026, the authority must be given written confirmation that the pipes have been removed or that an extension applies. And anyone who knows of lead pipes must inform the affected consumers without delay.

The statement “the test is due every three years” is wrong for a large proportion of those affected. For hospitals, nursing homes, schools, hotels and sports facilities — anywhere drinking water is supplied as part of a public activity — § 31 TrinkwV requires the test once a year. The Gesundheitsamt may extend the interval to three years under certain conditions, but that is the exception and requires a decision by the authority.

Above the action level, the water is not automatically shut off. What follows is a procedure: notification to the Gesundheitsamt, hazard analysis, measures, re-test. How far-reaching the intervention is — up to a ban on showering — is decided by the authority according to the level of the result and the risk situation; the result alone does not decide it.

Alongside the regulatory fine, there is a criminal offence: § 71 TrinkwV covers cases in which an infringement endangers health. That is a different category from a regulatory offence, and the reason why an abnormal result is not a piece of paper that can be set aside.

Avoid these mistakes

Common mistakes

Applying the three-year interval to public facilities. There, testing must take place once a year, unless the authority has granted an extension.

Treating the action level as a limit value. It triggers a procedure and does not shut off the water by itself.

Commissioning an unauthorised laboratory. The result then does not fulfil the obligation, however correct the figure may be.

Taking samples at only one point. The outlet, the circulation return and representative sampling points are prescribed.

Treating the lead-pipe deadline as having no exceptions. § 17 TrinkwV allows for extensions, for private installations until 12 January 2036.

Frequently asked questions

Questions and answers

How often must testing for Legionella take place?

That depends on the context in which the drinking water is supplied. For commercial activity — the normal case for rented residential buildings — § 31 TrinkwV requires testing at least every three years. For public activity, that is in clinics, care homes, schools, hotels or sports facilities, testing must take place at least once a year; the Gesundheitsamt may extend this interval to three years under certain conditions.

Is my house affected at all?

Only where three criteria coincide: a storage water heater with a capacity of more than 400 litres, or more than three litres of content in a pipe between the heater and the outlet, a shower or another fitting in which drinking water is atomised, and the building is not a one- or two-family house. If one of these is missing, the testing obligation does not exist.

What does exceeding 100 per 100 ml mean?

Annex 3 Part II TrinkwV lists this figure as a technical action level, not as a limit value. Exceeding it does not make the water unusable by operation of law, but triggers a procedure: notification to the Gesundheitsamt without delay, a hazard analysis, measures and a re-test. How far the authority intervenes depends on the level of the result.

Who pays for the testing?

The party under obligation is the operator of the installation, which in rented buildings means the owner’s side. The costs form part of the service charges and may be passed on to tenants — this follows, however, from tenancy law, not from the Drinking Water Ordinance, which regulates only the obligation itself.

How much is the regulatory fine?

The Drinking Water Ordinance does not set out its own amounts. Its § 72 declares infringements to be a regulatory offence within the meaning of § 73 IfSG; the general framework of up to €25,000 applies there. Where a danger to health is also present, the criminal offence under § 71 TrinkwV additionally applies.

Is it true that all lead pipes must have been removed since 2026?

Not in that shortened form. § 17 TrinkwV requires removal or decommissioning by the end of 12 January 2026, but it allows for extensions — among other things for private installations until 12 January 2036, where there is no danger to health. In addition, there is an obligation that is often overlooked: from 13 January 2026, the authority must be given written confirmation that removal has taken place or that an extension applies.

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Instruction under § 43 IfSG
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One-off, with no expiry

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