What Temperature to Set Your Water Heater, and How to Check It
Set a residential water heater to 120 degrees Fahrenheit (49 degrees Celsius). The U.S. Consumer Product Safety Commission (CPSC) urges all users to lower their water heaters to 120 F, and the U.S. Department of Energy's Federal Energy Management Program says that for most residential applications the temperature should be set at 120 F. This page covers the numbers, how to check your own tap, and the one situation where a hotter tank is used. Information is current as of October 2026.
1. Why 120 F
CPSC says the majority of injuries and deaths involving tap water scalds are to the elderly and children under age five. It gives these exposure times for most adults before third-degree burns:
| Water temperature | Exposure time |
|---|---|
| 150 F | 2 seconds |
| 140 F | 6 seconds |
| 130 F | 30 seconds |
| 120 F | 5 minutes |
The 120 F row is not "safe," only slower. CPSC notes that even at 120 F, a five-minute exposure could cause third-degree burns. Its advice is to never take hot water temperature for granted: always hand-test before using it, especially when bathing infants and young children. Leaving a child unsupervised in the bathroom, even for a second, could cause serious injuries, and CPSC calls your presence at all times the best defense against scalding.
CPSC adds that lowering the temperature conserves energy and saves money, and that you should consider the lowest thermostat setting that still satisfies the hot water needs of your clothes washer and dishwasher. It says a setting of 120 F may be necessary to reduce or eliminate the risk of most tap water scald injuries.
2. How to check the temperature at the tap
CPSC suggests holding a candy or meat thermometer under the faucet. For the most accurate reading, take it first thing in the morning or at least two hours after hot water was last used. If the reading is too high, adjust the thermostat according to the manufacturer's instructions and check again with the thermometer. The thermostat dial on the heater is a setting, not a measurement, so the thermometer reading at the tap is the number to go by.
3. How to lower it, by heater type
CPSC's publication gives a different starting point for each type of heater:
- Electric water heaters. Call your local electric company to adjust the thermostat, since some companies offer this service at no charge. Hot water should not be used for at least two hours before the setting is changed. To make the adjustment yourself, shut off current to the heater, then turn off the circuit breaker or remove the fuse that serves it. Most electric heaters have two thermostats, and both must be set to a common temperature for proper operation. You reach them by removing the upper and lower access panels. Adjust them following the instructions that came with the appliance, then check the water with a thermometer.
- Gas water heaters. Because thermostats differ, CPSC says to call your local gas company for instructions.
- Furnace-based hot water. If you do not have an electric, gas or oil-fired water heater, you probably have an on-line hot water system. Contact your fuel supplier to have the temperature lowered. CPSC says reducing the water temperature will not affect the heating capacity of the furnace.
- Apartments. Contact the building manager to discuss options for lowering your tap water temperature.
Work on an electric heater involves live wiring behind the panels. If you are not comfortable with that, the utility call that CPSC lists first is the simpler route.
4. When a hot tank is used: Legionella and mixing valves
The Department of Energy's Federal Energy Management Program notes that, under certain conditions, Legionella pneumophila (the bacteria that cause Legionnaires' disease) can grow in water heaters. The Department of Defense's Unified Facilities Criteria require storage tanks to be set no lower than 140 F to limit that growth, and at that temperature the bacteria can survive for less than a minute. That water also poses a risk of scalding, especially for young children and the elderly.
To handle both risks, the same criteria require a balanced-pressure-type tempering valve downstream of the tank for anti-scalding protection. For residential applications, the Department of Energy says to set that device, also called a mixing valve, to 120 F. In other words, a hot tank is only paired with a valve that brings the tap back to 120 F. Those criteria are written for federal facilities, so they are context, not a household rule. If someone in your home has a weakened immune system or a chronic lung condition, a doctor or a licensed plumber is the right person to ask about tank temperature.
5. Quick checklist
- Run the hot tap, hold a thermometer under it, and read the temperature first thing in the morning or two hours after last use.
- Aim for 120 F unless a medical or plumbing professional tells you otherwise.
- If you adjust an electric heater yourself, cut power at the breaker first and set both thermostats to the same temperature.
- Check the tap again with the thermometer after you change the setting.
- Hand-test bath water for babies and young children every time.
- Check your dishwasher and clothes washer manuals to see whether they need hotter water than 120 F.
6. Key takeaways
- CPSC urges 120 F; at 140 F an adult can be burned in about 6 seconds, at 120 F in about 5 minutes.
- Measure at the tap with a thermometer rather than trusting the dial.
- Electric heaters usually have two thermostats that must match, and gas and furnace systems are adjusted through the utility or fuel supplier.
- A tank held at 140 F for Legionella control should have a mixing valve set to 120 F downstream.