Legionella Testing of Drinking Water: Mandatory for Landlords in Neumarkt

Legionella bacteria in hot water systems pose a real health risk and are subject to clear legal regulations. For landlords in Neumarkt who operate apartment buildings with a central hot water supply, the Drinking Water Ordinance is binding-ignorance of the law is no defense against liability. This article explains the obligations, deadlines, costs, and reporting procedures for 2026.

Background: Legionella as a Liability Issue for Landlords

In recent years, several high-profile cases have shown that Legionella infections originating in rental apartments can lead to substantial claims for damages against landlords. Higher regional courts have held landlords liable for Legionella-related damages when the legally mandated testing intervals were not adhered to. The TrinkwV obligations are not mere red tape-they are the legal minimum standard, and failure to meet them leads directly to personal liability.

For property owners in Neumarkt who rent out apartment buildings, this means: Annual or triennial sampling is an investment of 300-600 euros that can avert six-figure claims for damages in the event of an emergency. Neglecting this obligation is simply economically unreasonable.

What are Legionella bacteria and why are they dangerous?

Legionella bacteria (Legionella pneumophila and related species) are bacteria that thrive optimally in hot water systems at temperatures of 25-50 °C. When inhaled via aerosols (shower spray, cooling towers, hot tubs), they can cause Legionnaires’ disease-a severe form of pneumonia with a mortality rate of 10-15% among at-risk groups (the elderly, immunocompromised individuals).

In rental buildings with a central hot water supply, ideal conditions for Legionella growth arise if the hot water is not kept at a constant temperature above 60 °C, if the piping contains dead legs (areas with no flow), or if the system has not been flushed regularly for a long time.

The legal basis is the Drinking Water Ordinance (TrinkwV, Sections 13-16 in conjunction with Annex 3, Part II), which applies to all operators of commercial drinking water systems.

Technical Prevention: The Most Important Measures

Prevention is more effective than reaction. These technical measures reliably prevent Legionella growth:

Maintain hot water temperature: At least 60 °C at the water heater outlet, never below 55 °C throughout the entire piping system. Thermostatic mixing valves protect tenants from scalding and are designed to limit the temperature at the tap to a maximum of 43 °C-but they do not prevent the piping system behind the mixing valve from becoming too cold.

Avoid dead-end pipes: Pipe ends without a drain are ideal breeding grounds for Legionella. If dead-end pipes are present in the system (e.g., due to renovations, vacant apartments), they must be flushed regularly or removed.

Regular flushing: Apartments that have not been used for more than 4 weeks (e.g., vacation homes, vacant units) should be thoroughly flushed before reoccupancy. Let water run through all faucets for at least 3 minutes.

Maintain showerheads: Showerheads are prime reservoirs for Legionella. Regular descaling (monthly) and replacement if necessary (every 2-3 years) are recommended. Showerheads should always be replaced when tenants change.

Overview of obligations: Who is responsible for what?

Obligation	Application	Deadline/Interval	Legal Basis
Initial inspection	New or modified system	Before commissioning	Drinking Water Ordinance § 14
Routine inspection	All rented apartment buildings with a central hot water system	Every 3 years	Drinking Water Ordinance § 14a
Risk analysis	If >100 CFU/100 ml	Immediately after results	Drinking Water Ordinance § 16
Obligation to report to the health department	If >100 CFU/100 ml	Immediately	Drinking Water Ordinance (TrinkwV) § 16 (1)
Tenant notification	If limit value exceeded	Immediately	Drinking Water Ordinance (TrinkwV) § 16 (3)
Operation Log	All systems	Ongoing	Drinking Water Ordinance § 15a

Source: Drinking Water Ordinance (TrinkwV), Version Q1 2026; DVGW Worksheet W 551 Drinking Water Installations; Bavarian State Office for Health and Food Safety (LGL) Enforcement Guide on Legionella, as of 2025.

The Drinking Water Ordinance makes no distinction between large and small apartment buildings: Anyone who operates a central hot water system and supplies water to others (tenants) is subject to this requirement. This applies equally to a 4-unit building in Neumarkt and a 40-unit property.

Practice: Conducting Legionella Sampling

Sampling must be performed by an accredited sampler in accordance with DVGW W 551 and Drinking Water Ordinance (TrinkwV) Annex 1. The following points must be observed.

Sampling Points: According to the Drinking Water Ordinance, representative sampling points in the piping network must be tested in larger systems-typically the hot water outlet at the water heater as well as individual taps in the distribution network (showerheads). DVGW W 551 provides guidance on the optimal selection.

Accredited Laboratory: Water samples must be analyzed in a laboratory accredited according to ISO 17025. There are several approved laboratories in the Neumarkt area; the Neumarkt Health Department provides a list of recommended service providers upon request.

Operational Log: According to § 15a TrinkwV, an operational log must be maintained in which all tests, measures, and notable findings are documented. In the event of an official inspection or a claim, the operational log serves as decisive proof that the landlord has fulfilled their duty of care.

Flushing Programs and Temperature Maintenance: Technical prevention is the most effective measure. Hot water should be ≥ 60 °C at the outlet of the water heater and ≥ 55 °C throughout the entire piping system. Dead-end pipes should be avoided or flushed regularly.

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What to do if limits are exceeded?

Exceeding the technical action level (100 CFU/100 ml) requires the operator to take immediate action.

Immediately: Notify the public health department (by phone, followed by written notification). In Neumarkt, the Health Department at the Neumarkt i.d.OPf. District Office is responsible (Health Protection Division).

Risk Analysis: A qualified expert (accredited drinking water specialist) must inspect the system and identify the causes. The costs range from 500 to 2,000 euros.

Remediation measures: Depending on the cause, thermal disinfection (flushing with water ≥ 70 °C), chemical disinfection (chlorine dioxide), or pipe rehabilitation may be considered. Costs: 500-10,000 euros depending on the system.

Informing tenants: Notify them in writing immediately as soon as an exceedance is detected and for as long as there is uncertainty regarding the safety of use.

Local Context: Neumarkt and Drinking Water Monitoring

The Public Health Department at the Neumarkt i.d.OPf. District Office is responsible for monitoring drinking water quality throughout the district. It conducts random inspections in rented apartment buildings and may also carry out unannounced inspections if necessary.

In Neumarkt, the drinking water systems in the neighborhoods surrounding the historic city center-south of the city palace and along the Altmühl-Naab lowlands-are predominantly more than 20 years old. Older systems with copper or steel pipes are more likely to develop biological deposits (biofilm), which serve as a breeding ground for Legionella. Owners of buildings constructed between 1960 and 1985 should monitor their systems with particular care.

For owners currently planning a heating or hot water system renovation (e.g., a heat pump with domestic hot water production), the renovation provides an opportunity to plan for Legionella-safe system temperatures and short piping runs from the outset.

Drinking Water and Property Value: If sampling reveals that Legionella limits have been exceeded and this is reported to the health department, a record is created that may become visible during a subsequent purchase inspection. Buyers and their financing partners are increasingly inquiring about the drinking water situation in the building. A clean sampling history is an underestimated quality feature in real estate appraisals in Neumarkt.

Legionella in Heat Pump Hot Water Systems

Modern heat pump systems with domestic hot water treatment have a particular connection to the issue of Legionella: brine-water heat pumps heat drinking water to 45-55 °C-a temperature range that does not reliably inhibit Legionella growth. Therefore, heat pump hot water systems must undergo regular thermal disinfection (heating to 60 °C once a week for at least 20 minutes).

This function is integrated into modern heat pumps as a “Legionella protection program” and runs automatically. After commissioning a new heat pump, owners should ensure that this program is active and documented. The operating log required under § 15a of the Drinking Water Ordinance (TrinkwV) must also be maintained for heat pump hot water systems if the building is rented out.

Costs of Drinking Water System Renovation: A Long-Term Investment

If Legionella testing reveals systemic causes-old piping, dead-end pipes, insufficient insulation-the question of a complete renovation of the drinking water system arises. This is an investment that pays for itself over the years.

For a multi-family home with 6 residential units in Neumarkt, a complete renovation of the hot water system (new pipes, modern water heater, circulation with pump and control system) costs between 15,000 and 35,000 euros. That sounds like a lot, but: The renovation cannot be passed on through operating costs; however, it can be charged to the tenants as a modernization measure under Section 559 of the German Civil Code (BGB) (rent increase of 8% of the annual investment costs). An investment of 25,000 euros thus justifies a rent increase of 166 euros/month for the entire building-distributed across 6 residential units, that’s approximately 28 euros/unit/month. Economically justifiable and clearly regulated by law.

Conclusion for Landlords in Neumarkt

Legionella testing of drinking water is a clear legal obligation for landlords in Neumarkt, not an optional service. The triennial sampling costs 300-600 euros-a very manageable expense relative to the liability in the event of a Legionella-related illness. The operation log, careful sampling, and immediate response to any exceedances of limit values are the three most important components of legally compliant operation.

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Sampling Protocol: What the TrinkwV Requires

Correct sampling is crucial-incorrect sampling can lead to false-negative results that mask the actual problem. The TrinkwV and DVGW Worksheet W 556 regulate the sampling protocol:

Cold water samples are taken as a first-run sample immediately after a prolonged period of stagnation (at least 8 hours). The sampler must not flush the faucet beforehand.

Hot water samples are taken according to the standardized VDI 6023 procedure: Sampling after a flushing period (until a constant hot water temperature is reached), documentation of the temperature at the sampling point and in the storage tank, transport temperature, and delivery to the laboratory within 24 hours.

Sampling must be performed by an accredited specialist company (in accordance with DIN EN ISO 19458)-samples taken by the property owner are not recognized. In Neumarkt i.d.OPf., there are several accredited water laboratories and HVAC companies with the appropriate certification.

Risk Assessment: When Is Immediate Action Required?

The Drinking Water Ordinance (TrinkwV) defines two limit values for Legionella in drinking water:

Limit Value	Concentration	Required Action
Technical action value	100 CFU/100 ml	Immediate notification to the health department, immediate investigation
Precautionary value	10 CFU/100 ml	Investigation of the cause, optimization of the system

If the technical action value is exceeded, the landlord is obligated to: immediately report the issue to the Neumarkt Health Department, immediately shut off or isolate the affected water system until the cause is resolved, inform tenants that the hot water is temporarily unsuitable for drinking, and commission a specialized company to analyze the cause.

The Neumarkt Health Department is responsible for issuing orders to take action when limit values are exceeded-and verifies whether sampling requirements have been met. Failure to maintain an operating log constitutes a separate offense subject to a fine under § 25 TrinkwV.

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Compiled by the my-home.de editorial team in collaboration with regional real estate analysts. Data as of Q2 2026.