Is 120 degree Fahrenheit ok for heater thermostat?

For a water heater, 120 °F (49 °C) is the factory setting, and is the low end of the heating scale. Most are set higher, at 130°F to 150°F to allow for the cooling of the water in the pipes. The hottest setting is about 160°F, which may be too hot for human use (showers) but suitable for washers and dishwashers.

In water heaters with two, an upper and a lower thermostat (which perform different functions), the upper thermostat should be left at 120°F.