As the heating season begins, hygiene experts, health authorities and professional associations in Germany are warning against a popular cost-saving measure: permanently lowering hot-water temperatures or switching off circulation can, in unfavourable conditions, increase the risk of Legionella contamination – and therefore of Legionnaires’ disease. The advice is based on current recommendations from the Robert Koch Institute (RKI) and the industry association DVGW as well as statements from several local health authorities.
Legionella bacteria prefer to multiply in warm, stagnant water or water that is rarely replaced. Infections usually occur through inhaling tiny water droplets, for example while showering. The RKI stresses that older or poorly maintained installations are particularly at risk. Although no simple, direct relationship between average hot-water temperature and case numbers can be established in general, maintaining the temperature is nevertheless considered a key element of prevention. The upshot: save energy, yes – but not at the expense of drinking-water hygiene.
Technical standards specify clear minimum temperatures. Centrally heated hot water should consistently reach around 60 degrees Celsius at the heater outlet. At typical taps, the temperature should reach at least 55 degrees Celsius after a short flush. Also important are a properly functioning hot-water circulation system, regular hydraulic balancing, the proper operation of storage tanks and pipes, and documented maintenance. Larger systems are also subject to requirements under the Drinking Water Ordinance, including periodic testing and measures to be taken if limits are exceeded.
For practical purposes, authorities and associations recommend a step-by-step approach: in one- and two-family homes with short pipe runs, a temporary, moderate reduction may be acceptable if usage patterns and temperature checks allow it. In apartment blocks, residential complexes or public buildings with centralised supplies, however, permanent reductions without professional guidance are risky. Operators should discuss planned energy-saving measures with a specialist contractor or the relevant public health department adjust, check temperatures at the tap and avoid interruptions to circulation.
Regardless of the type of system, regular use of all outlets, flushing infrequently used pipe runs, maintaining fittings and following generally recognised engineering standards all reduce the risk. If limit or guideline values are exceeded, or there is reason for suspicion, the Drinking Water Ordinance requires investigations, a risk assessment and appropriate measures to be initiated without delay. This makes it possible to balance hygiene and energy efficiency without endangering health.
Editor: Clara Simonichek (Article created with AI assistance).