How to Turn Up a Hot Water Heater: Find the Ideal Setting

Here is how to turn up a hot water heater, the ideal temperature settings for safety, and how to troubleshoot common issues.

Ideal Water Heater Temperature Setting

Most modern water heaters ship from the factory with a pre-installed temperature setting of 140 degrees Fahrenheit. While this ensures hot water, it poses a scalding risk. The Department of Energy recommends you set the temperature to 120 degrees Fahrenheit.

This setting provides water hot enough for showers and dishwashers but cool enough to prevent burns. It also slows mineral buildup and corrosion in your pipes.

Why not go lower?
While turning the dial down saves money, setting it below 120 degrees creates an environment where bacteria, such as Legionella (the cause of Legionnaires’ disease), can thrive. Keep it at 120 degrees to stay safe.

If you have a tankless water heater, like this Rheem RTEX-18, you get a continuous supply without maintaining a large tank of hot water. You still need to adjust the digital controls or knob to that 120-degree sweet spot for the best results.

Is It Bad to Turn Your Water Heater All the Way Up?

Yes, cranking the dial to the max is dangerous. It dramatically increases the risk of scalding, spikes your energy bill, and puts unnecessary pressure on the tank, which can shorten the unit’s lifespan.

Most water heaters max out around 140 to 160 degrees Fahrenheit. For context, a fresh cup of coffee is usually served at 160 degrees. You wouldn’t pour that over your hands, so you shouldn’t shower in it either.

Here is how quickly hot water can cause serious burns:

How to Turn Up a Hot Water Heater

The method for adjusting your temperature depends on whether you have a gas, electric, or tankless model.

Gas Water Heaters

Gas units are generally the easiest to adjust because the control is external.

1. Locate the dial at the bottom of the tank. It is usually red or black.
2. Note the current setting. Some dials have numbers, while others use “Warm,” “Hot,” and “Vacation.”
3. Rotate the knob slightly toward the “Hot” setting. If there is a specific notch for 120 degrees, aim for that.
4. Wait roughly one to three hours for the water in the tank to reach the new temperature before testing it at a faucet.

Electric Water Heaters

Adjusting an electric heater takes a bit more work. Most standard home units have two thermostats (upper and lower) concealed behind access panels. You must adjust both to the same temperature so one element doesn’t burn out trying to compensate for the other.

1. Turn off the power. Go to your circuit breaker panel and flip the breaker labeled “Water Heater” to the OFF position. This is critical for safety.
2. Remove the upper and lower access panels on the side of the tank using a screwdriver.
3. Peel back the insulation to reveal the thermostats.
4. Use a flathead screwdriver to turn the adjustment screw on both thermostats to 120 degrees Fahrenheit.
5. Replace the insulation and screw the access panels back on.
6. Turn the circuit breaker back on and wait about an hour for the water to heat up.

Electric Tankless Water Heaters

1. Locate the digital display panel on the front of the unit.
2. Use the “Up” or “Down” arrow buttons to set your desired temperature.
3. If your unit does not have a digital display, you may need to remove the cover and adjust a potentiometer knob inside (refer to your specific owner’s manual for this style).
4. Run the hot water tap for a minute to verify the new temperature output.

Gas Tankless Water Heaters

1. Find the digital remote or control panel, often mounted on the unit or a nearby wall.
2. Press the power button to ensure the interface is active.
3. Press the temperature adjustment buttons to select 120 degrees Fahrenheit.
4. Open a hot water faucet. The burner should ignite immediately, and the display may show the current output temperature.

How to Check the Water Temperature

Don’t rely on the dial on the tank, as they can be notoriously inaccurate. The best way to confirm your settings is to test the water coming out of the tap.

1. Go to the faucet closest to the water heater (usually the kitchen or a laundry sink).
2. Turn on the hot water and let it run for at least one full minute. This clears out any cold water sitting in the pipes.
3. Fill a cup or glass with the hot water.
4. Insert a standard cooking thermometer into the cup immediately.
5. If the reading is above 120 degrees, turn the heater down slightly. If it is below, nudge it up.

FAQs

How Long Does it Take for a Hot Water Tank to Heat Up?

For a standard tank heater, like this Bradford White model, it usually takes 40 to 60 minutes to recover after being fully depleted. Electric models typically take longer than gas models to heat the same volume of water.

What are the A-B-C Settings On a Hot Water Heater?

On many gas control valves, the letters represent specific temperature ranges. Generally, the “A” setting is around 120 degrees Fahrenheit, “B” is roughly 130 degrees, and “C” is approximately 140 degrees. “Very Hot” is usually 160 degrees.

How Can You Reduce Power Usage of a Water Heater?

To save energy, lower the temperature to 120 degrees, insulate the first few feet of hot and cold water pipes, and install a water heater blanket. If your unit is over 10 years old, consider upgrading to a high-efficiency model from brands like A.O. Smith or Whirlpool.

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Why Is My Water Lukewarm Even After Adjusting the Temperature?

If you have an electric heater, a lower heating element may have burned out, or the dip tube could be broken. For gas heaters, the burner orifice might be clogged. If adjusting the thermostat doesn’t fix the issue, you likely need a repair or a new component.

The Heat Is On

Knowing how to turn up a hot water heater gives you control over your comfort and your bills. By keeping the temperature at the recommended 120 degrees Fahrenheit, you protect your family from burns while ensuring the shower is always warm enough.

If you have tweaked the settings and still can’t get the right heat, it might be time to call in a pro to check for broken elements or sediment buildup.