My wife often tells me that I am in hot water. Actually, in most cases, that is an expression that refers to my poor behavior versus anything to do with water.
However, in the course of doing home inspections in Bellingham and Whatcom county, I often find water heaters that are set too hot -- the water temperature set so high as to lead to a high probability of a scalding burn.
In this photo, the water is almost 137 degrees F. To reduce the probability of a scalding burn, water should be set no higher than 120 degrees F. In order to get a burn, at 120 degrees, it takes several seconds. However, the higher the temperature is, over 120 degrees, the less exposure it takes to cause a serious burn that will require medical attention.
Water temperature can vary, depending on how recently the tank heated, so homeowners should check the hot water periodicially with a meat thermometer and have it adjusted so as to never exceed 120 degrees F. Usually, with a gas hot water heater, setting the temperature is as simple as turning a dial. At an electric water heater, a person is potentially exposed to high voltages at the internal thermostats, so setting such a tank should be done by a qualified person.