Legionella in the Real Estate Business

Legionella is a bacterium that can be found in drinking water in small amounts. They reproduce in warm water. The ideal growth conditions are provided at temperatures between 25 °C and 45 °C. Legionella growth is effectively inhibited at temperatures above 55 °C. Above 60° C Legionella can be effectively reduced. Therefore, in household drinking water installations, Legionella can be found in warm water in particular.

Water temperatures in water heaters were reduced in order to save costs, in turn leading to a rise in Legionella concentrations in the warm water. In order to protect consumers, annual Legionella testing was expanded beyond public buildings to also include commercially rented residential properties.

The testing mandate generally applies to buildings with at least three housing units where at least one of these units is currently rented. Furthermore, the property must have a central drinking water heater with a tank volume of more than 400 liters or more than three liters in the pipeline between outflow of the water heater and the farthest tap. Single family houses and duplexes are exempt from the testing mandate.

The testing mandate applies to housing units that are rented out commercially. Therefore, a condominium ownership association is only obligated to test for Legionella if one of the apartments connected to the drinking water installation is rented out. If none of the apartments are rented, Legionella testing is not required.

Monitoring the drinking water is an important duty that is performed either by a municipal health agency or by an authorized testing site. In order for an operator to fulfill the obligations stated in the German Drinking Water Ordinance, the drinking water testing must be carried out by a testing site that is authorized in accordance with §15 paragraph 4. The guidelines regarding various sampling standards and specific transport conditions must be followed. Taking the samples in accordance with the Drinking Water Ordinance is a task for trained professionals. As a private individual, if you would like to have your water analyzed for your own purposes? Our subsidiary, IVARIO, provides water testing for consumers. You can find further information here: IVARIO – Water Testing for Consumers

The samples should be taken at the following points:

• At the outlet of the drinking water heater (supply line)
• At the end of the circulation (return flow) (For this, the sampling point must be taken before the circulation pump in the direction of flow, not between the water heater and the circulation pump.)
• The tap furthest away from the drinking water heater for each rising pipe

Extraction taps that can be thermally disinfected (flame treatment) are to be affixed to the drinking water heater.

Extraction taps that can be thermally disinfected must be installed by a company specializing in this.

In general, the samples can be taken from the normal faucets. The faucet aerator should be able to be removed without a large amount of force. In properties with scalding protection devices, either these should be able to be bypassed or a freely accessible sampling valve should be mounted on the angle valve in the hot water pipe.

The drinking water installations listed in the section "Which drinking water facilities are affected by the testing mandate?" must be tested for Legionella every three years as long as they are rented out commercially.

The drinking water installation should be kept in operation properly. That means setting the drinking water heater (tank) to a temperature of 60 °C and ensuring that the circulation does not decrease by more than 5 °C so it maintains a minimum temperature of 55 °C. Aside from that, all taps should be in use. For cold water, that means usage at least every 3 days and warm water at least every 7 days. Pipes that are not used, i.e. stagnant water, should be avoided.

No. The costs of installing the drinking water heating system, including the extraction taps, cannot be apportioned.

The operational costs of the central drinking water heating system can be apportioned to the tenants insofar as the apportionment is contractually agreed upon. The sampling for the tests can be apportioned as part of the operating expenses. If the technical intervention values in the Drinking Water Ordinance are exceeded, then further Legionella tests will be necessary and these cannot be apportioned.

The German Drinking Water Ordinance stipulates a technical intervention value of 100 CFUs/100 mL. If this is exceeded, measures must be taken in accordance with § 16 paragraph 7 of the Drinking Water Ordinance.

Yes, the residents must be informed of the results of the preliminary testing. This requirement can be fulfilled simply by posting a notification in the main stairwell. It is not necessary to write individual letters to each tenant.

The health authorities can penalize violations of the German Drinking Water Ordinance with monetary fines of up to €25,000. If there is a verified case of legionnaire's disease in a tenant of a leased property, the landlord is liable to prosecution.