What number should your hot water heater be on?

Author: Otis Lang PhD  |  Last update: Thursday, July 31, 2025

120 degrees Fahrenheit is the safety recommendation against scalding, but 140° is the common default setting.

What temperature is the B setting on a water heater?

B - 140° F - Less than 5 seconds. A - 130° F - About 30 seconds. HOT - 120° F - More than 5 minutes.

Should my hot water heater be on AB or C?

They relate to the relative temperature of the hot water. C is hotter than B which is hotter than A. So if B is too hot, set it to A; if B is too cool, crank it up to C. Generally, A should be as hot as you need, but habits vary.

Is 130 too hot for a water heater?

In the US, the maximum legal temperature for a water heater in a residential setting is 120 degrees. Most folks want to run at 125-130 degrees but be careful. The Federal law that stipulates the max temperature is because of folks, especially kids, getting burned by the water.

What setting should my hot water heater be on?

The EPA recommends 120 degrees because it's hot enough to keep diseases at bay but not hot enough to cause scalding. This setting will also supply enough hot water for most small families and is relatively energy efficient.

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What does a and b mean on a water heater?

Understanding these settings can help when figuring out how to adjust the temp on water heater units. A typically represents around 130°F. B usually corresponds to 140°F. C indicates a temperature of about 150°F or higher.

What temperature is the C setting on a water heater?

That should be plenty hot enough for most uses in your home. Now, some water heater temperature controls come with settings that read “A-B-C” as opposed to numbers. Generally, A means 120 degrees, B means 130 degrees, and C means 140 degrees. Refer to your water heater's manual to confirm these settings.

Is it safe to set your water heater at 140?

Although some manufacturers set water heater thermostats at 140ºF, most households usually only require them to be set at 120ºF, which also slows mineral buildup and corrosion in your water heater and pipes. Water heated at 140ºF also poses a safety hazard—scalding.

Can you shower in 130 degree water?

According to Centers for Disease Control and Prevention (CDC), water temperatures ranging from 130 to 140 degrees Fahrenheit(°F) can eliminate most of the harmful bacteria. However, be warned that these high temperatures can also increase the risk of scalding.

Does turning up the water heater make hot water last longer?

Raising the temperature setting on your water heater ultimately makes your hot water supply last longer. It will ensure everyone gets a hot shower, with plenty leftover to run your dishwasher and washing machine.

What level should water heater be on ABC?

The next highest setting is usually either labeled as “Hot” or with a triangle, and this setting should correspond to 120 degrees. From there, you will typically see three higher settings marked either as 1, 2, and 3 or A, B, and C that correspond to 130, 140, and 150 degrees, respectively.

What temperature should hot water be for shower?

According to most dermatologists, the ideal shower temperature is anywhere between 98°F (37°C) and 104°F (40°C)—and no more than 105 °F (41°C). Rinsing under lukewarm water allows you to stay comfortable and maintain your body temperature while reaping all the benefits of both hot and cold showers.

What should a hot water system be set at?

Hot water needs to be stored above 60°C in hot water systems to prevent bacteria growth (such as Legionella), but a tempering valve ensures that the water comes out of the tap at a lower temperature.

Should your water heater be on AB or C?

These are usually labeled A, B, C or 1, 2, 3, and the last setting is always “Very Hot.” The A or 1 setting should be around 130 degrees, B or 2 is 140 degrees, C or 3 is 150 degrees and “Very Hot” is always 160 degrees. Again, we never recommend setting the unit above the B or 2 setting to prevent scalding.

How often should I flush my water heater?

Most homeowners should flush their water heaters every 6 months or so, but if you have extremely hard water, you may want to do it more often. Flushing your hot water heater could be necessary as often as every few months depending on the mineral content of your local water supply.

Why is my water not getting hot?

A lack of hot water can be caused by a variety of issues. In electric water heaters, a power loss or heating element failure can cause water to no longer heat in the tank. In gas water heaters, a faulty gas connection, a bad pilot light, or a bad burner can cause no water to heat.

Is 135 too hot for a water heater?

Water Heater Temperature Recommendations

120 degrees Fahrenheit is the safety recommendation against scalding, but 140° is the common default setting.

What temperature should I set my hot water tank to?

If the temperature is above 65°C, then the water will be too hot to use, and it increases the risk of serious burns. Keeping the temperature at a safe level, 60°C to 65°C, makes the water hot enough to use and hot enough to kill unwanted bacteria.

What is the highest safe water temperature?

There were two temperatures discussed for each fixture during the design standard meetings. One was the “use temperature” and the other was “the maximum temperature” to prevent scalding. It's generally agreed that 120 degrees Fahrenheit is the maximum safe hot water temperature that should be delivered from a fixture.

What is the best setting for a hot water heater?

Manufacturers often recommend a hot water heater temperature between 120 to 140°F, and there's a reason for this. The Occupational Safety and Health Administration (OSHA) recommends a recommended hot water temperature of at least 122 degrees to prevent the growth of harmful bacteria.

What happens if the water heater is set too high?

The primary way most people notice their water heaters overheating is because the water becomes unbearably hot, scaldingly so. If your water heater is set on too high a temperature, burns, and severe injuries may occur.

Is 140 too high for water heater?

The best temperature setting for a hot water heater is between 120 and 140 degrees. Below 120 degrees, bacteria can develop in the stagnant water sitting in the tank. Above 140 degrees, the water is so hot that you and your family members can be at risk for scalding in as little as two seconds.

What does ABC mean on my hot water heater?

Here is what temperature each letter stands for: Hot- 120 degrees. A- 130 degrees. B- 140 degrees. C- 150 degrees.

What temperature is Legionnaires disease in water?

What is legionella? Legionella bacteria is commonly found in water. The bacteria multiply where temperatures are between 20-45°C and nutrients are available. The bacteria are dormant below 20°C and do not survive above 60°C.

What temperature kills bacteria in a water heater?

It takes only 32 minutes on average for Legionella to die at temperatures of 140 degrees, and at 151 degrees, the bacteria will die instantly. This is why disinfection that uses temperature change will set a water heater to approximately 158 degrees for five minutes.

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