Rheem Water Heater Blinking Red Light – What Does It Mean?

Rheem water heaters are some of the most reputable ones in the HVAC industry. They're known for being reliable and long lasting. But what do you do if your Rheem water heater has a blinking red light? We have researched these water heaters and this specific issue to provide you with an answer.

A flashing red light on your Rheem water heater indicates that the heater has entered a lockout condition and needs attention. It's best to stop using the water heater until you resolve the issue with the flashing lights. The reasons for the issue can range from gas supply problems to electrical or temperature regulation issues.

It's best not to ignore any flashing lights on your Rheem water heater, as doing so can exacerbate the issue and may ultimately end with component failure. Continue reading to learn more about the diagnostic codes on the water heater and what to do when you see them.

A white water heater inside the basement, Rheem Water Heater Blinking Red Light - What Does It Mean?

Rheem Water Heater Diagnostic Codes

1 Flash

A single flash on your Rheem water heater means that the heater does not have access to the water supply or water in the unit at all. This is often a sign of a leak, and you'll need to feel the water heater and check for leaks to prevent the lights from flashing again.

2 Flashes within 3 seconds

If you see 2 lights flashing within 3 seconds, it means that the thermo-pile is having trouble sensing the voltage of the water heater. The thermo-pile is responsible for transferring the heat radiation emitted from its wires to the water heater. Think of it as the voltage supplier.

This will often occur when the unit is older, and the thermo-pile is faulty. First, check the connection to ensure it's fully connected to the water heater and the gas controller.

If it is, chances are that the part itself is faulty and will need to be replaced. Luckily, this part is fairly inexpensive and can be replaced in no time.

3-8 flashes within 3 seconds

If your Rheem water heater has 3-8 consecutive flashes within 3 seconds, it means that there is a serious issue with the unit. Here are the main things that will cause these error codes:

  • High water temperature limit tripped or failure
  • Water temperature sensor component failure
  • Gas control failure or issues with gas access
  • Issues with the pilot flame

In most of these cases, you'll need to contact a professional licensed HVAC technician to troubleshoot and repair the unit.

How do I reset my Rheem water heater?

Turning the water heater into high mode

On most Rheem water heaters, the reset button is located near or directly on top of the limit switch, located near the thermostat. Resetting a Rheem water heater is fairly straightforward. Here are the steps to do it:

  1. To reset the heater, turn off the power by flipping the power switch and the heater's switch at the circuit breaker.
  2. Next, remove the front panel of the heater to gain access to the limit control switch. Depending on the model, you may need to use a wrench or screwdriver to remove the nuts on the front.
  3. Once you locate the high limit switch, press the red button sitting in the middle of it. This is the reset button.
  4. Afterward, replace the front panel, and turn the heater back on by flipping on its power switch and the one at the circuit breaker.

Reasons To Reset Your Water Heater

Water heaters may malfunction due to quick outside temperature changes and other times due to malfunctions and electrical issues.

In many cases, a simple reset can fix the issue. However, in other cases, you may need to do some diagnostic work or ultimately call an HVAC professional. Here are a few reasons why you may need to reset your Rheem water heater:

  • Sometimes there may be an electrical supply problem with your water heater, and it receives no electricity. In most cases, you'll need to check the voltage of the electrical wires. Often, you'll need to reset the circuit breaker and the heater itself as well.
  • If you replace a fuse in your water heater because it has blown or tripped, you'll typically have to reset the water heater to turn the appliance back on.
  • If your Rheem water heater senses high temperatures, the temperature limiting control switch (also known as "ECO") may automatically turn off the heater to prevent the unit from failing. Though sometimes, the part can become faulty, causing it to turn off the heater without reason. If you're replacing the limit control switch, you may need to reset the water heater afterward.

Where is the pilot light on a Rheem water heater?

Water heater pipes and wirings properly installed to the basement wall

The pilot light for most Rheem water heater models is typically located on the front of the unit. Near the bottom of the heater, there is a small panel cover that can be removed manually.

The panel covers a window that's about 7 x 10 inches. Inside the window, you'll find the pilot. If you need to relight the pilot, here are the steps to do it:

  1. Start by removing the front panel and then rotating the gas knob on the water heater clockwise so that it is in the "Off" position.
  2. Next, turn the water temperature down counterclockwise to the lowest setting possible. Wait about 5 to 7 minutes so that any remaining gas near the pilot's gas supply can dissipate.
  3. After this time, turn the gas knob counterclockwise so that it is in the "Pilot" position.
  4. Next, press the red ignition button located on the side of the gas knob. And while pressing the button, hold the gas knob down until the pilot ignites. You may need to press the button a few times if your heater is older (you'll hear a clicking sound every time it's pressed). However, if it doesn't ignite after about 7 to 10 tries, wait a few minutes and then try again. If the pilot won't ignite, you may need to reach out to an HVAC technician for assistance, as there could be an issue with the unit. For example, the striker may need cleaning, or there may be a problem with the gas supply line.
  5. If the pilot light ignites, turn the gas knob to the "On" position, and replace the front panel or outer door of the pilot area. Next, turn the water temperature dial back up to your preferred setting. Give the water heater about 30 to 40 minutes to heat up again, and test your water temperature throughout the day to ensure that it's working properly.

How long does it take for a Rheem water heater to heat up?

On average, most gas water heaters will take anywhere from 30 to 45 minutes to fully heat all of the water in the tank. However, water heater sizes vary, and residential tanks can hold anywhere from 20 to over 900 gallons.

A water heater control panel mounted on the bathroom wall

The size of the water tank will affect how quickly it can heat the water inside of it, so it's normal for larger tanks to take a bit closer to 40 minutes to an hour to heat fully.

What setting should my Rheem water heater be on?

The best setting for your Rheem water heater will depend on your preference, though they usually leave the factory at a setting of 120 degrees Fahrenheit.

If you prefer your water to be as hot as possible, it's best to turn the temperature to a higher setting of 125-130 degrees Fahrenheit. The lowest setting on these water heaters is typically 90 degrees Fahrenheit.

And while setting the temperature lower than that will definitely save you money on your home's energy bill, it's important to note that this temperature setting can negatively impact the performance of your dishwasher and clothes washing machine.

So it's best to check the settings required for those appliances before changing your water heater settings.

Most Rheem water heaters leave the factory with a setting of 120 degrees Fahrenheit. To change the water temperature setting, you'll simply need to turn off the power to the water heater on the unit and at the circuit breaker.

Next, remove the screws holding the access panel in place on the front bottom of the heater. Finally, turn the water temperature dial to your preferred setting.

In Closing

A white water heater inside the basement

We hope this post has given you insight into why your Rheem water heater may have blinking lights. Remember, the first thing to do if you notice blinking lights on your water heater is to refer to your user's manual.

This is the quickest way to determine the error code that the heater is experiencing. And doing so can help you quickly diagnose and repair the problem or get help from an experienced technician.

Before you go, be sure to check out these other posts:

Rheem Water Heater Leaking—What To Do?

Portable Air Conditioner Leaking Water – What Could Be Wrong?

This Post Has One Comment

  1. Francisco

    I’m getting 9 red LED flashes then a pause then the 9 flashes. The blue LED flashes, I press the piezo starter, but then the red LED begins it’s 9 flashes
    What does the 9 red LED flash code mean? The article only covered up to 8 flashes.
    Thank you as the article was still informative.

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