Much has been debated over an optimal water heater temperature setting. Many sources, including ENERGY STAR, offer the energy saving factors of temperatures of 120 degrees or lower. And yes, there are savings to be had, but realistically for those whose current setting is closer to the standard factory preset temperature of 140 degrees.
On the other hand, not as many share information about the possibility of contracting Legionella bacteria with a lower setting, especially of that lower than 120 degrees. OSHA states some excellent precautions for preventing this.
Water Heater Repair Nashville’s conclusions are that it something that each family needs to weigh in terms of the health concerns primarily. For those with children or with elderly people in the home, a higher setting can be a water scalding concern. Conversely, those susceptible to contracting respiratory infections, a higher setting should be used.
Here is an infographic Phil Luther put together for us highlighting the different temperature growth ranges of Legionella.