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.
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.
120 degrees Fahrenheit is the safety recommendation against scalding, but 140° is the common default setting. Most experts agree that anything below 120 degrees creates a risk for bacteria to develop inside your water heater from stagnant water, such as legionella that causes Legionnaire's disease.
Adjust both thermostats to the same temperature setting. WARNING! Higher temperatures increase the risk of scalding. If you have increased the temperature setting above 120°F, install Thermostatic Mixing Valves at each point of use and set them to 120°F or lower.
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.
Set too high, or at 140ºF, your water heater can waste anywhere from $36 to $61 annually in standby heat losses. Additional savings will be realized by the lower temperature for consumption (from water demand or use in your home, such as clothes washing, showers, and dishwashing). These may amount to more than $400.
Use your best judgement for your family and household when setting the temperature. It's smart to stay within the range of 120 to 140 degrees Fahrenheit (49 to 60 degrees Celsius). Make an adjustment, test it out and repeat until you settle on the perfect temperature setting for you home and water heater.
During the winter months, an optimal temperature for domestic hot water is around 55-60 °C. This temperature ensures that the water is warm enough for showers and other needs, taking into account low outdoor temperatures.
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.
C - 150° F - About 1-1/2 seconds. B - 140° F - Less than 5 seconds. A - 130° F - About 30 seconds. HOT - 120° F - More than 5 minutes. LOW - 80° F - No hazard.
Many tank-style water heaters – particularly those powered by electricity and not natural gas – feature two thermostats because they have two heating elements.
If you have younger children in the house, you are always better to have your water heater set to 120 degrees to prevent scalding. If there are no kids in the home or your children are older, we would usually recommend turning the unit up to 130 or 140 degrees.
Turning up the heat at the water heater causes hotter water to go to the hot tap. If you desire the same temperature, this makes you use more of the cold tap. Therefore, you're using a smaller percentage of hot water for the same total shower flow. This makes the perceived hot water in your tank last longer.
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.
Thermostat Replacement
Each heating element has its thermostat; if those don't work, the elements won't either. Hiring a pro to replace a thermostat averages around $150 to $200. The part itself costs up to $20 and is easily replaceable without disturbing other components if you have some DIY experience.
Put one probe from the multimeter on the reset terminal (beside the reset button) and the other probe on the left side terminal, which will be the one with power wires. If the multimeter's reading says 1, then the water heater thermostat most likely needs to be replaced. If it reads 0, it is functioning normally.
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.
Turning your water heater off completely when it's not in use can help you save a small amount of money each month on your energy bills, but the hassle of manually turning your unit off and on typically outweighs the benefits.
No hot water – This most likely indicates a problem with the upper thermostat. Not enough hot water – This likely indicates a problem with the upper thermostat. Slow hot water recovery – This is another problem that can occur when the lower thermostat is malfunctioning.
The thermostat on your hot water cylinder should be set between 60 and 65 degrees. Setting it any higher than this means you're using more energy than is needed. Not only that, but you risk scalding yourself when using the hot water tap or shower.
Temperature Is Too High
The most obvious reason for a high water heater gas bill is if the temperature is set too high. According to experts, most homeowners should keep water heater temperatures between 120 and 140 degrees F.