Stainless Steel Legionella

By Milou de Jong

Stainless steel is the #1 choice for sinks, faucets, and shower heads. You might have them at home, but also in healthcare, hotels and other industries it is a firm favourite. Although stainless steel is considered to be durable and it looks clean, it may still be a bacterial paradise. According to research, stainless steel encourages the growth of Legionella bacteria.Your stainless steel shower head, where you enjoy your long hot showers, might be putting you at risk for Legionnaires’ disease. In this article we will discuss how stainless steel influences legionella growth based on scientific research; and, we will make an objective comparison of Legionella prevention techniques that could counteract this.

Research Stainless Steel & Legionella

Over a period of 4 years, a group of Dutch scientists tested stainless-steel faucets compared to traditional brass ones. The results of their study showed that the stainless steel coating degrades within a few years, leaking iron into the water. Iron water poses perfect conditions for Legionella growth. Causing the stainless steel faucets to triple the bacterial rate of Legionella (> 100.000 kve/L). 1

One of the scientists, van der Lugt said: “Stainless steel faucets corroded within just four years, producing the iron which we think led to an increased Legionella growth. (…) It solves a mystery for me, of why I always found these bacteria in showers with thermostatic faucets [stainless steel] but less in showers with more traditional ones.” 2

Corrosion of Stainless Steel

The degradation of the stainless steel coating can be induced by two types of corrosion: galvanic corrosion and microbiologically-influenced corrosion (MIC).1 Galvanic corrosion is caused by iron rust which is naturally present in drinking water systems due to the rusting of cast iron distribution pipes. MIC happens when biofilm is present in the water installation.3 Biofilm is a slimy layer of microorganisms, the breeding ground for Legionella, that is attached to the pipework. The biofilm influences the corrosion in your pipework.3

Legionella prevention techniques – corrosion & biofilm

The presence of Legionella in water systems is a major concern. Choosing the right Legionella prevention technique depends on several factors. The study shows that the type of material influences the growth of Legionella.1 Legionella prevention techniques that deteriorate the pipework potentially increase Legionella growth instead of decrease (due to higher iron rust concentrations). Hence, techniques, such as, chlorine dioxide, chemical shock, chlorine, and anodic oxidation simply fan the flames of the Legionella problem.

As biofilm influences the corrosion of stainless steel coatings it is important that the Legionella prevention technique completely dissolves the biofilm. Copper silver ionization is the only technique that both removes biofilm and is non-corrosive for your pipework. Therefore, the best solution for your stainless steel appliances! 

References:

  1. van der Lugt, W., Euser, S. M., Bruin, J. P., Den Boer, J. W., Walker, J. T., & Crespi, S. (2017). Growth of Legionella anisa in a model drinking water system to evaluate different shower outlets and the impact of cast iron rust. International journal of hygiene and environmental health, 220(8), 1295-1308.
  2. Allen, V. (2017, August). Do stainless steel sinks raise risk of Legionnaires’? Retrieved from https://www.iol.co.za/lifestyle/health/do-stainless-steel-sinks-raise-risk-of-legionnaires-10985001
  3. Corrosionpedia. (n.d.). Biofilm. Retrieved from https://www.corrosionpedia.com/definition/1649/biofilm