What Do the Letters on My Water Heater's Dial Mean?

You already understand how adjusting the cold and hot water taps changes the temperature of the water coming out of the faucet. But did you know there's also a water heater dial to control how hot your water gets? This little dial is usually at the bottom of the tank and has several letters.

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What Do the Letter Settings on My Water Heater's Dial Stand For?

The letters on the dial are the water heater temperature settings. Most water heater dials have the letters "A," "B" and "C" as well as words such as "HOT," "VERY HOT," "LOW" and "VAC." You may also see an "OFF" setting. "HOT" is the normal setting on most water heaters and is around 120 degrees Fahrenheit.

The settings "A," "B," "C" and "VERY HOT" generally correspond to the following temperatures:

• A: 130 degrees Fahrenheit

• B: 140 degrees Fahrenheit

• C: 150 degrees Fahrenheit

• VERY HOT: 160 degrees Fahrenheit

"VAC" stands for vacation, and this setting lowers the water temperature to warm instead of hot. Switching to this setting helps you save money on the cost to heat the water when you won't be home to use it.

What Letter (Temperature) Should I Set My Water Heater Dial At?

In most cases, you should set your hot water heater thermostat to "HOT," as this generally corresponds to 120 degrees Fahrenheit (49 degrees Celsius). This temperature ensures the water is hot enough to prevent harmful bacteria growth in the tank. It also helps reduce sediment buildup, which can decrease efficiency.

If you like a hot shower, it may sound like a good idea to adjust the water heater temperature higher, but this can be a safety risk. At 120 degrees — the normal hot water temperature — it takes more than 5 minutes of contact with the water to cause second- or third-degree burns on an adult. Bumping this up just another 10 degrees shortens the time to around 30 seconds. If you have children, seniors or anyone in your household with mobility problems, turning the water heater up too high can pose a serious scalding risk. Doing so also drives up your energy bills.

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• How Your Water Heater Works

• A Tankless Job? Decide Whether a Tankless Water Heater Works for Your Home

• The Age-Old Question: Is My Water Heater Gas or Electric?

• How Do I Turn My Water Heater On?

Temperature Settings: Why Is My Water Too Hot or Not Hot Enough?

Adjusting the water heater dial is the easiest way to fix an issue with too hot or too cold water, but if you're continuing to have issues, there could be a larger problem. If you run out of hot water before you finish showering or filling the bathtub, there could be a leak in the hot water line or sediment buildup in the tank. The more sediment in the tank, the less space there is for water. This issue is more common with older water heaters.

If there's no hot water even with the dial on "HOT," it could mean the pilot light is out or the heating element is malfunctioning. If your water is too hot even after you turn down the dial, it could signal a problem with the thermostat.

If your water heater isn't keeping the correct temperature, diagnosing the cause and fixing the problem is a job for a licensed technician. Both gas and electric water heaters have delicate components and can also pose safety hazards.

• Gas water heater repairs should be handled by technicians who are trained to work with burners and combustion systems.

• Electric units often have high-voltage wiring and can be extremely dangerous to work on without the right training, correct tools and safety equipment.