Rule of thumb is safe bathing and showering temperature is 100 degrees Fahrenheit. That means your heater hot water temperature should be set at or below 120 degrees Fahrenheit. Sometimes water heater thermometers vary depending on the brand, the age, or how much the water heater is used.
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.
"Hot water is typically described as approximately 110 to 140 degrees," says Channa Ovits, M.D., FAAD, a Westchester, New York-based board-certified dermatologist at Westmed Medical Group, a Summit Health Company. But in terms of a shower, you should never tiptoe over 120 degrees, due to the chance of a burn injury.
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.
The maximum Department of Energy recommended water heater temperature setting you should never exceed is 140 degrees Fahrenheit. The lowest recommended setting should never be below 120 degrees Fahrenheit.
So, What Is the Ideal Shower Temperature? “Luke warm,” says Anolik. Many experts agree the tepid temperature feels slightly warm compared to your body temperature, and falls somewhere between 98º and 105º F.
Water Heater Temperature Recommendations
120 degrees Fahrenheit is the safety recommendation against scalding, but 140° is the common default setting.
To help prevent bacteria growth, the ASSE recommends keeping the water in your water heater tank at about 135 - 140 degrees Fahrenheit.
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.
For most houses, 80 psi (pounds per square inch) is about right. If the water pressure is over 100 psi, that's too much. This increase in pressure is usually the fault of the municipal water company, which sets the pressure higher in order to accommodate fire hydrants and tall commercial buildings.
Hot Water Baths
For those who relish a hot water bath to unwind, dermatologists suggest a peak temperature of around 44.4°C (112°F). However, it is advised not to exceed 48.9°C (120°F), as extreme temperatures can lead to skin irritation or even burns.
Many accidents involving scalding have been fatal and have mainly occurred during bathing or showering. Where vulnerable people are at risk from scalding during whole body immersion, water temperatures must not exceed 44°C. Any precautions taken should not introduce other risks, for example from legionella bacteria.
Even though a water temperature of 110° F is 'relatively-safe', exposure can be painful; the human pain threshold is around 106-108° F. As the chart reproduced below reveals, the severity of a burn is a function of the temperature of the water and the duration of the exposure and the condition of the skin.
Most adults will suffer third-degree burns if exposed to 150 degree water for two seconds. Burns will also occur with a six-second exposure to 140 degree water or with a thirty second exposure to 130 degree water. Even if the temperature is 120 degrees, a five minute exposure could result in third-degree burns.
If you are taking a shower or a bath you can receive severe burns because of scalding hot water. At 140°, water takes only a few seconds to cause third-degree burns, which penetrate the skin and can create permanent scarring.
Hot water is typically about 130 degrees Fahrenheit or warmer. Between 90 and 110 degrees is considered warm water. And water temperature between 60 and 80 degrees is cold.
OSHA, on the other hand, recommends setting your water heater to 140 degrees in order to aid with cleaning and sanitation. Anything between 120 and 140 degrees is within the safe range, which means it really all comes down to a matter of personal preference.
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.
The temp you are leaning toward is scalding hot and could hurt some one. If you have a mixing valve installed, the tank needs to be about 20 degrees hotter than the mix valve setting. So 140- 145 is adequate, with a 120 setting on the valve. Unless you need more drawdown, no need to go above 140 or so.
The average adult uses about 10 gallons of water per shower (at a rate of 2 gallons of water per minute). If you assume that an 80-gallon tank has about 55 gallons of hot water to dispense before refilling, that means you have 27 or so minutes of total shower time before running out of hot water.
The ideal water heater temperature should strike a balance between preventing scalding accidents and providing comfortable hot water. According to experts in plumbing and home safety, a recommended temperature range of 120-130 degrees Fahrenheit is generally considered safe for most households.
By setting your hot water heater at 120F, the water will be too hot for bacteria to grow. Keeping your water this hot will effectively kill off any bacteria and completely eliminate this health concern.
Lloyd-Smith and Mendelssohn [6] found the pain threshold to be 44.6°C (112.3°F). Defrin et al. [7] investigated heat pain threshold across the body and found the lowest level in the chest (42°C or 107.6°F), the highest in the foot (44.5°C or 112.1°F) and the hand was 43.8°C (110.8°F).
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.
120 Degrees is the recommended max temperature for water heaters, according to both the American Society of Sanitary Engineering and the US Department of Energy. Firstly, setting the max temperature to 120 degrees prevents the water from scalding your skin.