The Danger of Orange and Yellow Flames in Water Heaters and What you Can do About It

gas burner flameGas burner flame
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Why is my water heater flame orange and yellow? What to consider when it comes to water heater troubleshooting?

Here we'll talk about gas water heaters and the danger of orange and yellow flames that develop due to improper (incomplete) gas combustion.

See how typical flame color looks like, what you can expect when the gas is not burning correctly and how it can affect you.

In general:

  • Blue flame - OK
  • Red/orange flame – check it out (it should turn blue after it burns dust and dirt).
  • Yellow/orange flame – requires attention. Get it checked by the professional.

A word about gas water heaters

Gas water heaterGas water heater

Every gas water heater generates heat by burning natural gas or propane and releases exhaust gases. They use gas burners to heat water and require a sufficient amount of combustion air.

The burner is located inside the combustion chamber, and with the help of the vent system, combustion products are vented to the outdoors. While some models are equipped with the pilot light to light the gas burner, others use a hot surface ignitor – HSI.

Gas water heaters are usually equipped with a small opening found at the bottom of the unit, and where you can visually inspect the flame, is it ON or OFF, is it burning with the blue, yellow or orange glow, and is it stable or is flickering.

Proper (complete) gas combustion

Proper gas combustion means that the flame is blue and stable and is getting enough oxygen. The blue flame is usually accompanied by some tiny yellow tips.

When you see a blue flame, you will know that your gas burner produces less pollution, there is no high carbon monoxide (CO) emission, less soot is present, and the flame provides the highest temperature, making it very efficient. The temperature of the flame is around 3,600 F.

Improper (incomplete) gas combustion

The main indications of the improper combustion are yellow, orange, and red flame, including irregular flame patterns and high flame. That means the flame is starving for oxygen.

An orange flame, for example, has a much lower temperature of around 1,800 F, resulting in less efficient heating, a higher amount of soot, and an increased amount of carbon monoxide. Other warning signs include unusual smell, eye irritation, and higher energy bills.

An orange flame occurs when dust and dirt are burning, while a yellow flame happens when the flame is burning with no air going in, resulting in excessive smoking and soot.

On the other side, too much air can cause the gas burner to lift off and operate with noise.

Note: Soot, as a product of incomplete combustion, is a fine black/brown carbon powder that often sticks to the chimney or a vent pipe.

Important: Improper combustion should be fixed ASAP because the flame is dangerous and could release poisonous carbon monoxide gas. Note that carbon monoxide is colorless, tasteless, and odorless that can cause illness and lead to death. It is known as the "silent killer."

With the first sign of an orange or red flame, contact your local HVAC technician to fix the problem.

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What causes the water heater flame to burn with the orange and yellow colors?

As we mentioned, orange and yellow flames are usually an indication of insufficient air supply, and where the products of combustion re-circulate, contaminating the surrounding air.

Scale buildup. Remove all the deposits from the gas burner and orifices.

Venting issues. Your chimney or a vent system can also cause incomplete gas combustion. They might not be working correctly, designed, installed, or maintained. The same applies to a water heater.

Reduced airflow. There might also be some obstructions in the passageway, reducing or blocking the airflow. Issues such as an uninsulated chimney, deformation in the venting pipes, corrosion, and condensation can also lead to an inadequate draft and lack of oxygen in the combustion chamber.

Negative pressure. During the heating season and when other devices also operate, the amount of air inside the house gets disturbed and often depressurized, which means negative pressure. As the atmospheric vent uses the buoyancy, the heated air goes back instead of going out, affecting the normal heating operation.


Regardless of the gas type device, you always want to see a blue color flame. And if there is a tiny tip of yellow, don't worry, it is OK.

Natural gas and propane require a proper air-to-gas ratio to burn the gas entirely without causing safety issues.

Remember, by increasing the oxygen supply, you get complete combustion, while you have only problems due to the lack of oxygen.

It is important to keep your gas water heater in healthy working condition so that it can perform well, heat water efficiently, and provide safe, reliable, and durable operation. The easiest way to check whether your heater is delivering proper or improper combustion is by checking the burner flame color and shape.

As mentioned in the text, blue flames indicate higher temperatures, efficient burning, and complete combustion. If you see yellow, orange, or red flame color and it is not stable, your gas burner needs adjustments or cleaning. Or replacement. Turn your water heater off and contact your local HVAC pro.

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