Hot water has been around since man first harnessed the power of fire, but when at elevated temperatures it is dangerous and even deadly. Today’s hot water heaters offer a diverse range of technologies that perform leaps and bounds ahead of their predecessors, but what temperature should they deliver? Some facilities may simply set the heater to a usable temperature, but while this may seem like an acceptable practice, there is an issue that needs to be addressed: Legionella.
One of the biggest concerns for hot water systems in commercial buildings is legionella bacteria. Legionella is a bacterium that enters the human body by inhalation and aspiration of water droplets and is responsible for Legionnaire’s Disease, a bacterial infection of the lower respiratory system that often gets misdiagnosed as pneumonia; one in 10 people who contract Legionnaires Disease will not survive. Figure 1 shows a legionella growth chart, which displays their growth behavior. These organisms live and multiply in water between 68-122° F, and thrive in water 95-115° F. At 121° F, legionella bacterium stops multiplying, but is still present in water.