Is Superheating a Potable Water System After Positive Legionella Results Effective?

You’ve just received your Legionella analysis and the results show percent positivity above 30%.  What do you do?  You decide to superheat and flush the system by raising the temperature of the water above 140 degrees (also known as thermal eradication).  How effective is this procedure?  You won’t know until the retest results come back.  You receive the results and they are good, no positives.  The next round of testing approaches, the samples are collected, the results are in and you’ve got more positive Legionella results!  Why?   The answer is because after superheating the water, the biofilm is still there, you have not removed it; what you have done was kill whatever was in the bulk water, but unfortunately the biofilm is still there.  The organism thrives on the biofilm, it’s their nutrition, it’s what they live on.  Superheating and flushing will not penetrate and remove the biofilm.  If you don’t penetrate and remove as much of the biofilm as possible, you are going to continue in a vicious cycle of superheating and flushing, testing, and receiving positive Legionella results.

Now what do you do?  Should you superheat and flush again?  Should you try something different?  Your water treatment company suggests performing a chlorine dioxide disinfection.  What is chlorine dioxide?  It’s a chemical compound that consists of one chlorine atom and two oxygen atoms, it creates a gas that dissolves in water.  Once injected into the water system it will begin to penetrate and destroy biofilm.  There is never a guarantee that Legionella will not return after a chlorine dioxide disinfection, however, by using chlorine dioxide you have greatly increased the chances of removing bio-film and the source of the Bacteria, as opposed to super-heating which only provides superficial results.

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