BOOK SERVICEWhat temperature should my hot water be to prevent burns?
To prevent tap water scalds, the hot water at your taps should be no hotter than about 49°C (120°F). At this temperature, it still feels hot, but it takes much longer to cause a serious burn, especially for children and older adults. In most homes, that means lowering your water heater temperature and/or installing mixing valves so water comes out of the tap at a safe temperature.
TL;DR
- Water at 60°C (140°F) can cause severe burns in just one second, especially in children.
- Aim for about 49°C (120°F) at the tap to reduce the risk of scalds while still having comfortably hot water.
- Test your hot water with a thermometer and lower your water heater temperature if it is too hot.
- If you have an electric water heater or anyone with serious health conditions at home, ask your doctor and plumber before changing the setting.
- Installing mixing valves lets you keep the tank hot enough to limit bacteria while delivering safer water at the tap.
Can tap water really cause serious burns? Yes. Most Boston hot water heaters are set to a temperature of around 60°C (140°F). Water this hot can severely scald a child’s skin in just one second.
A scald is a second-degree or third-degree burn caused by hot liquid or steam. Hot coffee, tea, soup, and other hot foods are the most common causes of scalds to young children. Hot tap water is a less common cause, but these scalds are often more severe—and they are easy to prevent.
To help prevent tap water scalds, the hot water at all your taps should be no hotter than 49°C (120°F). At this temperature, it takes much longer—about 10 minutes—to burn a child’s skin instead of just a second or two.
Tap water scalds can happen anywhere that the water is too hot, not just in the bath. Children have been scalded by hot tap water when playing at the sink, or by putting their hands or feet into a bucket filled with hot tap water for household cleaning.
Why children and older adults are at higher risk
Children are more at risk for tap water scalds because:
- A child’s skin is thinner and more sensitive than an adult’s skin, so it burns more quickly.
- Young children cannot move away from hot water quickly, especially in the bath or at the sink.
If the water is too hot, a child can get a deep burn that covers a large area of the body and may require surgery and skin grafts over time.
Elderly people and people with certain disabilities or medical conditions (such as diabetes) are also at higher risk. They may not feel heat quickly or may have trouble moving away from hot water in time.
How to test your hot water temperature
You can easily test your hot water with a thermometer:
- Use a thermometer that can show higher temperatures, such as a meat or candy thermometer. Run the hot water tap for about two minutes at the hottest setting. If you have used a lot of hot water in the past hour, wait two hours before testing.
- Fill a cup with the hot water and place the thermometer in the cup.
- Wait 30 seconds and check the temperature. If it is higher than 49°C (120°F), you should lower your water heater temperature or consider installing mixing valves.
How to lower your hot water temperature safely
The simplest way to reduce scald risk is to lower your water heater temperature so water at the tap is closer to 49°C (120°F). Do this only if you can easily see and adjust the thermostat dial on the outside of the tank, and always read the manufacturer’s manual first.
If anyone in your Boston home has a long-term or serious illness, talk with their doctor before lowering your water heater. Do not lower the water heater temperature if anyone in your home has health conditions such as:
- Chronic obstructive pulmonary disease (COPD)
- HIV/AIDS
- A history of organ transplant
- Cancer
- A weakened immune system (from disease or medications that suppress the immune system)
These conditions can increase the risk from bacteria such as legionella, which can cause legionnaires’ disease, a type of severe pneumonia.
Adjusting gas and oil-fired water heaters
- Gas and oil-fired water heaters usually have thermostat dials located on the outside of the tank.
- If the dial has numbers, turn it down to about 49°C (120°F). If the dial has words like Hot, Warm (or Medium), and Vacation, turn the dial to the Warm or Medium setting.
- Do not lower the temperature of your water heater below 49°C or below a Medium setting. A lower setting can encourage the growth of bacteria like legionella.
- After adjusting, wait 24 hours and test the tap water again. It may take a few adjustments to get it right.
Special precautions for electric water heaters
If you have an electric water heater, do not lower the temperature setting below 60°C (140°F). The design of many electric tanks can make them more prone to legionella growth at lower temperatures.
In that case, you can still improve safety at the tap by installing mixing valves. These devices blend hot and cold water so that the water coming out of faucets is no hotter than about 49°C (120°F), even though the tank stays hotter to help limit bacteria.
Using mixing valves to control tap temperature
Mixing valves (also called tempering valves) are installed in your plumbing and control the temperature of the water before it leaves your taps. Inside the water heater, the temperature can remain high enough to limit bacteria, while the valve mixes in cooler water as needed so water at the tap is safer.
Talk to a licensed Boston plumber about installing mixing valves. There are three main ways to use them:
- Install a master mixing valve at the water heater to control tap temperature throughout the home.
- Install mixing valves on the hot water pipes going to specific areas, such as the bathroom and kitchen.
- Install mixing valves at individual taps, such as each sink and bathtub.
The cost of installing mixing valves depends on how many you add and whether other plumbing work is being done at the same time.
What if you live in an apartment or multi-unit building?
Turning down the thermostat on large water heaters in multi-unit buildings is generally not recommended, because lower tank temperatures can increase bacterial growth and may leave residents without enough hot water.
If you do not have access to your building’s water heater:
- Ask your Boston landlord or property manager to ensure that the hot water at your taps is no hotter than about 49°C (120°F). They may be able to install mixing valves in the hot water pipes serving your apartment.
- If mixing valves cannot be installed, you can still use other devices to help reduce the risk of tap water scalds, especially for children and older adults.
Other devices that help prevent tap water scalds
In addition to lowering your hot water temperature or installing mixing valves, you can use:
Anti-scald or shut-off devices: These attach to the faucet or replace the faucet completely. If the water gets too hot, they reduce the flow to a trickle until cooler water is mixed in.
Tap guards: Tap guards block a child’s access to the hot water tap, which can help prevent accidental burns during bath time or play.
Does lowering hot water temperature increase the risk of bacteria?
Lowering water temperature does raise questions about bacteria like legionella, which causes legionnaires’ disease. These bacteria can grow in indoor plumbing systems, especially in hot water tanks at certain temperatures.
For most healthy people, lowering hot water temperature to about 49°C (120°F) at the tap is not a concern when done correctly and with proper precautions. However, you should:
- Avoid lowering the household water heater thermostat below 49°C (120°F).
- For electric water heaters, keep the thermostat at 60°C (140°F) or higher and consider installing mixing valves instead of lowering the tank temperature.
- Consult a doctor before making changes if anyone in the household has a serious or long-term illness or a weakened immune system.
Is 49°C (120°F) hot enough for cleaning and bathing?
Yes. Most daily cleaning and bathing tasks do not require hotter water:
- Comfortable bath water is usually between 37°C and 40°C.
- Modern laundry detergents and washing machines can clean effectively at lower water temperatures.
- In the kitchen, you can sanitize cutting boards and surfaces with a mild bleach solution (for example, 1 teaspoon of bleach in 3 cups of water).
Will I run out of hot water more quickly?
Most households do not notice a big change in hot water supply after lowering the thermostat slightly. If you regularly run out of hot water, it may be a sign that you need a larger water heater or a different type of system, rather than hotter water.
Will I save money on energy costs?
Hot water tanks use a significant portion of your home’s energy. Lowering the water heater from about 60°C (140°F) to around 49°C (120°F) can reduce your energy use, although some savings may be offset if you use more hot water.
In many homes, you may still see modest savings each year. Adding an insulating blanket to the water heater can also reduce energy use further.
What if we need very hot water for allergy or asthma concerns?
Some households wash bedding at higher temperatures to control dust mites and allergens. If you need very hot water for laundry, you can still protect your family from tap water scalds by:
- Keeping the water heater at a higher temperature for the clothes washer line.
- Installing mixing valves for bathroom and kitchen taps to lower water temperature in those areas.
- Using dust mite control additives or high-heat machine drying cycles as alternatives.
If you have questions about setting a safe hot water temperature, installing mixing valves, or upgrading your system, talk to a licensed Boston plumber for guidance specific to your home and family.