Turn off power to the water heater at the breaker if it is electric
Turn the gas control knob to a higher temperature setting if it is gas
Remove the access panel on an electric water heater
Lift the thermostat cover insulation
Use a flathead screwdriver to adjust the thermostat higher
Set both upper and lower thermostats to the same temperature on an electric unit
Replace the insulation and access panel
Restore power to the electric water heater
For a gas water heater, set the temperature dial to a higher setting
Wait several hours for the water to heat
Test the hot water at a faucet before adjusting further
Keep the temperature at or below 120°F unless a higher setting is specifically needed