Super-Chlorination for Legionella Control: Why It May Not Be Enough

On this, our Legionella control systems website, we have discussed whether hyperchlorination, also called super-chlorination, is an effective Legionella treatment. Hyperchlorination is a popular approach for remediating Legionella, but there are valid concerns as to whether hyperchlorination is a good overall choice for Legionella control.

As the New York State Department of Health has noted, Legionella growth following hyperchlorination can rebound, meaning that bacterial levels can return quickly, and at higher levels than originally detected. This is a great concern and a valid reason to avoid hyperchlorination when attempting to control Legionella.

If hyperchlorination does appear to be effective in the short-term, there is good reason to think that it will not provide an effective long-term solution. A recent example: Bacteria that causes Legionnaire’s disease was found at in the barracks at Joint Base San Antonio-Fort Sam Houston (JBSA) in September 2022 during routine water testing. This was not the first time Legionella had been discovered in the barracks: it had been discovered and treated just one year prior. The treatment: super-chlorination (hyperchlorination). Following the super-chlorination, Legionella tests were negative throughout the year, but then Legionella was detected again just one year later.

As a truly independent Legionella control company, we aren’t surprised by this result for two reasons:

  • Legionella is naturally occurring in nature. It is possible that Legionella bacteria could be reintroduced to the plumbing system at any time.
  • More likely, Legionella that was present in biofilm was never fully eradicated during the super-chlorination. Super-chlorination/hyperchlorination typically treats only the surface of the biofilm, struggling to destroy the Legionella found deeply in the plumbing systems’ biofilm.

We dive into this topic more deeply in our article, “When Legionella Remediation is a Waste of Money“. As noted in that article, the legal liability of an organization may be greater after treating Legionella through a simple hyperchlorination.

Given the reasons above, we typically do not recommend hyperchlorination as a Legionella control option. We also do not recommend heat and flush for similar reasons.

What do we recommend? As a truly independent Legionella Control consultant, we don’t have a stock answer because your facility is unique in its plumbing characteristics, water temperatures, climate, age, and incoming water quality. A Legionella risk assessment provides the only real answers. Many companies will skip the Legionella risk assessment because they have limited treatment options or don’t have proper training or certification for Legionella and pathogen control: when you only have one tool, there is no point in discussing other options.

A Legionella risk assessment is to your advantage. While there is a small cost associated with it, the Legionella risk assessment pays out quickly because it has the potential to reduce your treatment costs, a recurrence of Legionella, and your legal liability. A Legionella risk assessment protects your occupants and you. It also provides a baseline or an update for a water management program.

We are happy to help you navigate the process of determining the best Legionella control approach for your facility. Our goal is for you to have effective short-term and long-term Legionella control at the best possible cost. That’s the benefit of working with the truly independent Legionella experts at Nancrede Engineering Company. Contact us today to learn more.

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