According to the Federal Emergency Management Agency:
The U.S. Consumer Product Safety Commission urges all users to lower their water heaters to 120 degrees Fahrenheit.
A thermostat setting of 120 degrees Fahrenheit (49 degrees Celsius) may be necessary for residential water heaters to reduce or eliminate the risk of most tap water scald injuries. Consumers should consider lowering the thermostat to the lowest settings that will satisfy hot water needs for all clothing and dish washing machines.
Never take hot water temperature for granted. Always hand test before using, especially when bathing children and infants.
How to test your water temperature:
1. Run the hot water for five minutes.
2. Put a reliable thermometer that registers at least 150 degrees under the water stream.
3. If your water is more than 125 degrees, lower the thermostat on your water heater. If you can't find the temperature controls or have any questions, call a qualified contractor or your landlord for help.