The Great Water Heater Temperature Setting Debate

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.

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Tags: Debate, Heater, Nashville, Repair, Setting, TN, Temperature, Water


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Comment by Phil Luther on March 1, 2014 at 3:50am

Excellent questions Brad!  Let me share a document from the World Health Organization here that goes into much detail in terms of your first two questions.  I personally concur with final conclusion of saving energy from turning up the water heater setting.  I have young children so for me the risk of too high a setting is my determining factor on the topic.

Comment by Brad Cook on February 28, 2014 at 3:39pm

And what, exactly, is the risk of Legionella in your water supply? 

How does the Legionella get into your water heater (water supply)?

If 140 deg. is a burn hazard and a mixing valve is required (which often fail in HOT position), aren't you now contaminating your hot water with untreated (cold) water at the mixing valve?

I do not find any conclusive studies linking Legionella to domestic water systems in the US, particularly in private wells. In addition, according to the NIH (National Institute of Health), UV light is as effective as heat in killing Legionella bacteria. So why are we wasting so much energy cranking up our hot water temperature?

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