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There is an article on National Institute of Health from a public health organization in Montreal, QC, Canada. It conducted a study and of many water heaters tested, it found many electric water heaters set to 120F to be a hazard for growth of Legionella inside the tank. Interestingly it did not find any contamination in fuel burning types.
They've always recommended 120F for burn safety and energy conservations, but this organization recommends 140F in electric units for biological safety. I suppose another option is for 140 to 150F and a thermostatic blender (or whatever its called) at the water heater to combat the biological safety and scald issues. With the reduction in amount of volume of hot water needed by storing it hotter, I suppose you could mitigate energy concerns by going with a heater a size smaller than one you would use if you were to set it to 120F.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2094925/
They've always recommended 120F for burn safety and energy conservations, but this organization recommends 140F in electric units for biological safety. I suppose another option is for 140 to 150F and a thermostatic blender (or whatever its called) at the water heater to combat the biological safety and scald issues. With the reduction in amount of volume of hot water needed by storing it hotter, I suppose you could mitigate energy concerns by going with a heater a size smaller than one you would use if you were to set it to 120F.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2094925/