To lower the water temperature on your Rheem MR40245 Marathon 40 Gal. Electric Water Heater, you’ll need to adjust the thermostats manually. Here’s how to do it safely: Steps to Adjust the Temperature - Turn off power at the circuit breaker to avoid electrical shock. - Remove the access panel(s) on the side of the unit—there may be one or two, depending on whether your model has single or dual heating elements. - Peel back the insulation to reveal the thermostat(s). - Use a flathead screwdriver to turn the thermostat dial to a lower setting. The factory default is usually 120°F (49°C). - Replace the insulation and panel, then restore power at the breaker. Safety Tips - Never set the temperature below 120°F if you’re concerned about bacterial growth (like Legionella). - If you have small children or elderly individuals in the home, you might consider a setting closer to 110°F for added safety. - Always test the water temperature at the tap after adjusting.