I adjusted my narrative for mixing valves to include info on bacterial growth. Thought I would share and see what folks think.
Do you recommend a mixing valve if one is not installed?
There was a temperature mixing valve installed at the water heater. These mixing valves are typically installed to allow the water heater to be operated at or above 140 degrees F to kill bacteria such as Legionella. Legionella is an aquatic bacteria that thrives in warm water environments, and can cause Legionnaires Disease. It is commonly found in potable water supplies, hot tubs, cooling towers, fountains, swimming pools, etc. and multiplies in warm conditions especially between 68 to 122 °F. The Legionella bacteria can spread to humans when breathed in. We recommend setting the temperature of the water heater to 140 degrees F and adjusting the mixing valve so that the water delivered to the home is in the generally acceptable range of 110 to 120 degrees F to prevent scalding hazards while protecting against Legionella. Also note that most electric water heaters have energized electrical components at the temperature adjustment area and should be adjusted by a qualified person in accordance with the water heater manual operating instructions.