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

Are you wondering why your water heater flame is orange or yellow?

In this discussion, we’ll explore the potential dangers of incomplete gas combustion in gas water heaters.

Learn how to recognize typical flame colors and what to do if you notice a red/orange or yellow/orange flame.

Blue, yellow and red flame: gas burner

While a blue flame is normal, a different color flame may require professional attention for proper water heater troubleshooting.

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 heaters use natural gas or propane burners to heat water and produce exhaust gases, which are vented outdoors. The gas burners are located in a combustion chamber that requires adequate combustion air. Some models use a pilot light, while others use a hot surface ignitor (HSI) to ignite the gas burner.

To ensure proper functioning, gas water heaters usually have a small opening at the bottom of the unit where you can visually inspect the flame. It’s crucial to check if the flame is on or off, burning with a blue, yellow, or orange glow, and whether it’s stable or flickering.

Additionally, the vent system should be regularly checked and maintained to avoid any potential safety hazards.

Proper (Complete) Gas Combustion

Proper or complete gas combustion occurs when the gas is burned efficiently, resulting in a blue and stable flame that’s receiving sufficient oxygen. A blue flame indicates that the gas burner is burning fuel completely with minimal byproducts or emissions. The presence of some tiny yellow tips is normal for a blue flame.

A blue flame is indicative of the gas burner producing less pollution, emitting lower levels of carbon monoxide (CO), generating less soot, and providing the highest temperature, making it highly efficient. The temperature of the flame can reach around 3,600 F.

Improper (Incomplete) Gas Combustion

The main indication of improper combustion is a yellow, orange, or red flame, which includes irregular flame patterns and a high flame, indicating that the flame is not getting enough 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 an 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 hand, 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 vent pipe.

It is essential to fix improper combustion as soon as possible because the flame can be dangerous and release poisonous carbon monoxide gas. Carbon monoxide is colorless, tasteless, and odorless, and can cause illness and death, earning it the nickname of “silent killer.”

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

What Causes a Water Heater Flame to Burn With Orange and Yellow Colors?

As mentioned earlier, orange and yellow flames are often indications of insufficient air supply, resulting in combustion byproducts recirculating and contaminating the surrounding air.

Other factors that may contribute to improper gas combustion include:

Scale buildup. Deposits on the gas burner and orifices can impede proper combustion and should be removed.

Venting issues. A poorly designed, installed, or maintained chimney or vent system can also cause incomplete gas combustion. This applies to water heaters as well.

Reduced airflow. Obstructions in the passageway, uninsulated chimneys, deformation in venting pipes, corrosion, and condensation can reduce or block airflow, resulting in inadequate draft and lack of oxygen in the combustion chamber.

Negative pressure. During the heating season, other devices operating in the house can disturb the air and create negative pressure, which affects the normal heating operation. This disturbance can cause heated air to go back instead of going out, adversely affecting the atmospheric vent that uses buoyancy.

It is crucial to address any issues related to improper gas combustion promptly, as they can be dangerous and release poisonous carbon monoxide gas. Carbon monoxide is a colorless, tasteless, and odorless gas that can cause illness and lead to death. As soon as you notice an orange or red flame, contact your local HVAC technician to fix the problem.


For any gas-powered device, a blue flame is always desirable. A tiny yellow tip is also acceptable, but if there’s too much yellow, orange or red, it may indicate an issue.

Both natural gas and propane require the correct air-to-gas ratio to ensure safe, complete combustion. Increasing the oxygen supply will ensure complete combustion, whereas a lack of oxygen can cause problems.

It is crucial to keep your gas water heater in good working order, as it ensures efficient heating and safe and reliable operation. Checking the color and shape of the burner flame is the easiest way to tell if your heater is undergoing proper or improper combustion.

A blue flame indicates efficient burning, complete combustion, and higher temperatures. If you notice a yellow, orange, or red flame that is not stable, your gas burner requires adjustment, cleaning, or replacement. Turn off the water heater and call your local HVAC professional for assistance.


Why Is It Important to Have a Blue Flame in a Gas Water Heater?

A blue flame indicates that the gas is being burned efficiently and completely, which leads to lower emissions, less soot, and higher efficiency. It also indicates that the heater is safe to use, as there is no risk of carbon monoxide buildup. Conversely, a yellow flame in a gas water heater may produce unsafe levels of carbon monoxide, which can be harmful or deadly. It is advised to turn off the heater and seek professional repair or replacement.

Can the Smell of Gas Indicate an Improper Burning Flame in a Gas Water Heater?

Yes, the smell of gas can indicate an improper burning flame in a gas water heater. When the gas is not burned efficiently, it can produce a gas odor, indicating that the gas is not being completely burned. The smell is usually a sulfur or rotten egg-like odor added to natural gas to help detect gas leaks. If the gas is not burned efficiently, it can produce higher levels of unburned gas, which can escape and cause a gas leak.

This can be caused by a number of issues, including a lack of oxygen or a clogged burner orifice. In any case, if you smell gas, you should turn off the gas water heater immediately and contact a professional for repair or replacement.

Can a Gas Water Heater With a Yellow Flame Be Repaired?

Yes, in many cases, a gas water heater with a yellow flame can be repaired by cleaning or adjusting the burner. However, if the heater is old or has significant damage, it may be more cost-effective to replace it.

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