Knowledge / Building services
Legionella testing: duties for rented apartments
Central hot water systems in apartment buildings must be tested for legionella regularly. Who is affected and what happens if the result is positive.
Who is obliged
The Drinking Water Ordinance requires testing where drinking water is supplied as part of a letting, showers are installed and a large-scale water heating system is in operation. A system counts as large if the tank holds more than 400 litres or a pipe between heater and tap holds more than three litres.
In an owners’ association it is enough for a single apartment to be let. The association is then the obligated party, and the manager organises the testing. Systems in single- and two-family houses are exempt.
How often and by whom
Testing is due at least every three years. Samples are taken and analysed by an approved laboratory. The costs form part of the hot water supply costs and can be passed on to tenants where the tenancy agreement provides for it.
When the action value is reached
The technical action value is 100 colony-forming units per 100 millilitres. If it is reached, the health authority must be informed without delay. The cause must then be clarified, a risk assessment drawn up, the necessary remedial measures taken and the residents notified.
Prevention means sufficiently high temperatures, as a rule at least 60 °C at the tank outlet and 55 °C in the circulation return, hydraulic balancing and regular use of every tap.
This article provides general information and does not replace legal advice in an individual case. We are happy to advise you personally on your property.