Atwood Water heater

[countrypair]

On a recent trip, we noticed our water heater was producing really hot water! I checked the water heater & of course there is no adjustment for temperature. I contacted Atwood & they said the water heater is set for 140 degrees (way to hot & could scald a child). Most residential heaters are set for 120 degrees (option to increase by owner). Atwood suggested an adjustable thermostat, but my research has revealed these arn't reliable.
Any suggestions short of replacing the heater? Has anyone installed a mixing valve? If so where?
Thanks for any input.

[RV Wizard]

A mixing valve can be installed on the back side of the heater provided you have a little (4") space for the valve and inter connecting lines. Be sure to filter water before it enters the coach or you will have to be running some vinegar through to keep the valve from getting frozen from scale.