Useful Information


Legionella are waterborne bacteria that can proliferate under favourable conditions (temperatures between 25 and 50° Celsius) in drinking water installations in buildings or in  evaporative cooling systems. For humans, however, it only becomes dangerous when Legionella enter the lungs through nebulisation when inhaled, e.g. when showering. This can lead  to legionellosis, a dangerous form of pneumonia. It is a notifiable but non-human-tohuman infectious disease which, in the worst case, can lead to death.

The Robert Koch Institute registers up to 1,000 reported cases of legionellosis per year in Germany, of which approximately 5% ended in death. Many sources assume a very high number of unreported cases in the range of 15,000 to 30,000 diseases a year, which were not recognized as such and can even be assumed to have a mortalty of up to 10%.


„Legionella circuit“

A periodic and temporary temperature increase to over 60°C in a hot water system is called a "Legionella circuit". However, according to DVGW W 551 (A) and W 557 (A), this is not a thermal disinfection. This measure is not effective anymore if Legionella is already present. It also leads to rapid calcification and wear of the fittings and seals; it contributes to the development of resistance of Legionella to ever higher temperatures.


Biofilm - Protection and food for Legionella

Biofilm is a symbiotic community of microorganisms such as bacteria, fungi or algae. It uses the metabolic properties and protective mechanisms of other species and serves as a food base and protective zone for Legionella and amoeba, which in turn act as hosts for Legionella.

Stagnation, dead strands or oversized pipes and storage tanks, insufficient water exchange, too low hot water temperature <60°C or too high cold water temperature >20°C favour the biofilm growth.


Duties of the owner/building operator

The responsibility of the water supplier ends at the handover point of the building, the water flowmeter. Within buildings, however, germs can rapidly multiply through warming up and biofilm in pipes. Since 2011, regular Legionella tests have been required by German law for large systems with showers and a storage tank of more than 400 litres or a pipeline volume of > 3 litres between the outlet of the water heater and the tapping point.

It is therefore the duty of all owners/operators to design, modernize or retrofit their water piping systems in such a way that Legionella have as little chance as possible. If the limit value for Legionella of 100KBE/100ml specified in the Drinking Water Ordinance is exceeded, it can be assumed that there are defects in the drinking water system or its operation and that measures are necessary.


Requirements for a Legionella examination

  • Sampling and analysis of the test only by specially trained and certified personnel
  • Annual analysis for large public facilities
  • every 3 years for large private and commercial buildings
  • immediately in case of illness or special anomalies


Measures for hygienic water piping systems in buildings

For Legionella measured values above 10,000KBE/100 ml, immediate measures must be taken to avert danger - the German health authority may ban showering, shock disinfection,  etc.

If the limit value of 100KBE/100ml is exceeded, the following measures are recommended:

  • Registration at the health authority, information to owner / tenant
  • Immediate shock disinfection and optionally subsequent permanent disinfection

Already frequently used as effective and non-hazardous disinfection, newtec provides the solution with electrolysis in a compact nt-BlueBox, which enables immediate reduction by shock disinfection and subsequent active protection against Legionella by long-term disinfection.

  • Re-examination of Legionella
  • Hazard analysis with suggestions for corrective measures including a remediation plan for operational, constructional and procedural procedures.


Comparison of hazard classes of different disinfectants

According to Regulation (EU) No 528/2012 (Biocidal Products Regulation) the employer/operator is obliged under paragraph 14 to replace the disinfectant used with less dangerous ones as priority.


Advantages of nt-BlueBox over thermal disinfection

  • simultaneous disinfection of cold and hot water strands possible and cost-effective, which is often necessary and practised
  • active protection with nt-BlueBox against the release of millions of Legionella when removing biofilm or bursting unicellular organisms
  • efficient and continuous biofilm degradation through depot effect
  • no risk of scalding as with thermal disinfection with at least 70°C and 3 minutes at each shower head or tap
  • no heating of adjacent cold water strands and thus more risk of Legionella in cold water
  • low staff costs, low energy and operating costs
  • avoidance of heavy limescale deposits in the pipeline system, especially critical in areas with hard water
  • avoidance of possible temperature resistance of Legionella


Advantages of nt-BlueBox over ClO2 -dosing

  • avoidance of hazardous substances and high safety requirements, risk of explosion when handling the 2 components for ClO2 production on site
  • avoidance of harmful chlorite and chlorate by dosing of ClO2 as end product in reaction with biofilm
  • precise online monitoring of disinfectants and by-products not possible by dosing of ClO2


Advantages of nt-BlueBox over dosing of NaClO (15%, usual in trade)

  • safe disinfection by avoiding the decomposition of the active ingredient during storage at retailer and in warm environments (cellar)
  • avoidance of toxic chlorates due to decomposition of active ingredients during prolonged storage
  • less odour and more neutral in taste
  • prevention of hazard and safety requirements for storage, transport and dosing of 15% NaClO as hazardous substance


Advantages of nt-BlueBox over membrane electrolysis

  • lower investment and operating costs with low maintenance costs
  • without NaOH as a by-product of membrane electrolysis, which must be removed and disposed safely
  • less chlorate formation than in membrane electrolysis
  • simple, robust technology with intelligent measurement and control technology
  • "Plug & Play" or easy integration of the compact nt-BlueBox into existing sanitary installations