Should I set my water heater to AB or C?

The AB or C setting on your water heater refers to the dial markings on many Rheem and A. O. Smith gas water heaters where the temperature is not marked in degrees but in letters. On these gas control valves, the settings typically correspond to approximate temperatures. Low or Warm is around 80 to 90 degrees, Hot is around 120 degrees, A is about 130 degrees, B is about 140 degrees, and C is about 150 degrees, with Very Hot around 160 degrees. For most households, you should set your water heater to Hot or the triangle symbol, which corresponds to 120 degrees Fahrenheit. This is the recommended setting by the Department of Energy and most manufacturers because it provides comfortable hot water for showers and dishes while minimizing scalding risk, reducing energy costs, and slowing sediment buildup and tank corrosion. Setting it to A is 130 degrees, which is hotter and increases scalding risk, especially for children and elderly, and uses more energy. Setting to B at 140 degrees is sometimes recommended if you have a dishwasher without a built-in heater or if you need to kill Legionella bacteria, but it significantly increases scalding risk and requires a mixing valve for safety. Setting to C at 150 degrees is generally too hot for residential use and should be avoided unless you have a master mixing valve. Stick to 120 degrees for safety and efficiency.