As you consider how to conquer and prevent Legionella in your commercial water heater, you may have already heard of a variety of common tools such as chemical water treatment, pH balancing and disinfection. However, what temperature you keep the water at in your water heater also plays a significant role in the growth (or death) of Legionella bacteria.
Higher temperatures are less favorable for Legionella, but they can also pose a health and safety risk to humans. In order to understand the ideal temperature for your commercial water heater, you need to evaluate the risk to humans vis-à-vis the deadly zone for Legionella.
How Legionella Proliferates
Legionella is a bacteria that lives in freshwater, which means that your commercial water heater is not immune from an outbreak. When water is tepid, Legionella can thrive and multiply quickly, becoming a health risk. The ideal range of temperatures for Legionella tends to be between approximately 77 degrees to 113 degrees Fahrenheit.
However, one common misconception is that they will die outside of this range, which is untrue; while they thrive best within these tepid water temperatures, it takes more than moving your water heater to 114 degrees to kill Legionella.
Temperature To Stress Legionella
At 122 degrees, Legionella will become stressed enough to stop multiplying because the conditions are no longer favorable. However, between 122 and 130 degrees, the bacteria will remain present and will not die. In order to begin to kill Legionella, your water temperature must be set to 131 degrees or higher.
Temperature To Kill Legionella
At this minimum temperature, Legionella will begin to die off within five or six hours. It takes only 32 minutes on average for Legionella to die at temperatures of 140 degrees, and at 151 degrees, the bacteria will die instantly. This is why disinfection that uses temperature change will set a water heater to approximately 158 degrees for five minutes.
Risks Of High Water Temperature
The solution to Legionella may seem clear-cut based on the previous evidence; set your commercial water heater to 151 degrees and never worry again about the bacteria. Unfortunately, 151 degrees is well within the dangerous range for humans, and any water that is routed to a tap or contact point for humans should not be this hot. Temperatures ranging from 150 to 155 degrees can severely burn human skin after just a single second of exposure, which means that maintaining a commercial water heater at this temperature is not recommended.
Even 130-degree water can cause a serious burn after only 30 seconds. This means that you will likely need to keep your water heater turned down lower than the minimum required temperature to kill Legionella bacteria. One possible solution is to introduce point-of-use mixing valves that will lower the water temperature once it reaches its tap.
Protecting People Of High Water Temperature
You may also consider occasional water heater heat disinfection by turning off the use of all taps that come into human contact for a portion of the day and turning the water heater temperature up to 158 for at least five minutes. This will purge the water of Legionella, which die instantly at this temperature, so that the heater does not need to maintain this scalding water level consistently.
Inconsistent Temperatures Can Be A Problem
If you have found a temperature that works for your system, remember that Legionella is robust; if your water system contains vulnerabilities such as dead legs or inefficient pumps, the line could be experiencing inconsistent water temperatures that foil your well-thought plans for Legionella control.
This is why it is critical that you work with a Legionella professional who can review not only your water heater but your entire water system to ensure that any vulnerabilities and risk factors are controlled and repaired. Legionella that find safety from the heat in cooler water pockets and surface vulnerabilities will not die during regular heat-based disinfection and can cause an outbreak when you least expect it.
Seek Assistance From Our Water Treatment Professionals
Whether you are considering what the ideal temperature for your commercial water heater could be or you would like an expert to review your system and help you develop a plan for Legionella prevention and control, be sure to rely on professionals who have years of experience in the field.
Legionella Compliance Solutions would be happy to help you explore your options and evaluate the right temperature at which to keep your commercial water heater in order to prevent an outbreak of Legionella. Reach out to schedule an appointment to discuss your next steps to keep people safe from scalding water without giving bacteria a foothold to grow.