Effective protection against Legionellae

Legionella - a challenge for building operators

Water should always be clean, soft, and germ-free. This is of particular importance from a hygiene and health point of view. Especially in hotels, gastronomy, swimming pools and clinics, but ultimately in all buildings, the unlimited availability of hygienically perfect and well-tempered water is essential for the comfort and health of people. As diverse as the priorities for the provision of water are within the different building categories, so are the technologies of the water heating systems. Operators face technical, legal, organisational, and economic challenges in the same way.

The danger of Legionellae spreading proves that water is a sensitive topic. We would like to present the hygienically impeccable supply of water combined with the technical capabilities for minimising the risk of Legionellae on this page in detail.

What are Legionellae, where do they originate and what makes them so dangerous?

Legionellae are rod-shaped bacteria that find optimal living and reproduction conditions in a temperature range of 25 °C to 50 °C in fresh and salt water. They become inactive after a few minutes at temperatures above 60 °C. Legionellae can cause the "Legionnaire's disease" Legionellosis leading to serious diseases. Infections are caused by the inhalation of Legionellae in combination with water vapour, for example when taking a shower. Swimming pools and adventure pools, sports centres, nursing homes, kindergartens, hospitals, hotels, and residential buildings are particularly considered to be risk groups among commercially used buildings. People with weakened immune systems are particularly at risk. Whether drinking water, cooling tower, fountain, or wet separator, they all carry the risk of becoming a source of Legionellae infections.

Legionellae bacteria are particularly associated with the following technical systems:

  • Hot water supplies  
  • Ventilation systems, in particular air conditioning systems and humidifiers
  • Swimming pools, especially whirlpools
  • Plants that atomise water, such as mist generators and mist fountains

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What are the methods for protection against Legionellae in drinking water plants?

There are four different ways of Legionellae elimination. The first three methods - chemical disinfection, UV disinfection and membrane technology - basically work independently. The building automation and control system (BACS) is designed to enhance operational safety by switching on operating and fault signals and alarming in the event of malfunctions.

The fourth method of protection against Legionellae is thermal disinfection, which is carried out by

  • temporary thermal disinfection by means of anti-legionellae circuits
  • or permanent thermal disinfection.

The effectiveness of thermal disinfection can significantly depend on the building automation and control system (BACS).

Temporary thermal disinfection by means of anti-legionellae circuits

The so-called anti-legionellae circuit is a periodic, thermal disinfection as a preventive measure against Legionellae contamination. In this process, the drinking water storage tank and the entire hot water pipe network including the tapping fittings are heated to 70 °C for 3 minutes in a predetermined cycle. All outlet fittings are opened, which is normally done manually. Modern building automation and control systems comprise the capability to open the fittings automatically, considering the relevant safety precautions (protection against scalding).

The effective implementation of the anti-legionellae circuit is carried out by the building automation and control system which reliably controls and logs the required plant conditions.

Permanent thermal disinfection

Permanent thermal disinfection is based on a multi-stage drinking water heating system using the flow-through principle with a thermal disinfection section that permanently kills Legionellae.

The hot drinking water circulation flows through the reaction tank with continuous thermal disinfection in the temperature range of approximately 70 °C. The circulation itself is set to the specified flow temperature of 60 °C.

Since permanent thermal disinfection is more or less a continuous flow heater without a storage tank, the speed and function of the hot drinking water temperature control, which is implemented by or with the assistance of the building automation and control system, depending on the system, is of utmost importance.

GFR is your solution provider for efficient Legionellae protection


Take advantage of the following benefits:

  • Building automation systems from GFR master temporary disinfection and permanent disinfection
  • We ensure hygienically perfect water and compliance with drinking water hygiene
  • Implementation of hygiene requirements and regulations
  • Optimum protection against infection
  • Automated monitoring
  • Reduced expenditure of time
  • Reliable flow through the pipes
  • You will benefit from our over 40 years of expertise

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Take advantage of our expertise

GFR is your single point of contact for all questions, starting with planning, through implementation, optimisation and maintenance of your buildings.



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