Much has been discussed over exactly what is an optimal water heater temperature level setting. Many sources, consisting of ENERGY STAR, offer the energy conserving elements of temperature levels of 120 degrees or lower. And yes, there are cost savings to be had, however realistically for those whose current setting is closer to the standard factory preset temperature of 140 degrees.
Conversely, fewer share info about the possibility of contracting Legionella bacteria with a lower setting, particularly with a temperature lower than 120 degrees. OSHA specifies some outstanding precautions for preventing this.
Valid conclusions are that it is something that each family should weigh in regards to potential health concerns mainly. For those with kids or with elderly people in the house, a higher setting can be a water scalding concern. Conversely, those susceptible to contracting respiratory infections, a higher setting ought to be used.