Water Heater Burner Flame Problems and Repair Tips

Why checking the burner flame in water heaters is important? What should you do if the flame has a yellow, orange or blue glow? What are the most common problems if the gas is not burning correctly and how to avoid it? How does the normal flame color and shape look like?

Every gas-powered and tank-type water heater uses the gas burner located in the combustion chamber to heat water, pilot light or electrode to light the fire, and gas control valve to deliver natural or propane gas.

During the burning process, exhaust gases are vented out, either naturally (convection) or forced (electric blower). Therefore, tank-type water heaters are divided into atmospheric, power, direct and power direct models.

Most of the models have a viewport (opening) at the bottom of the unit where you can check the condition of the gas burner, how does the flame look like, and does it require any action or not.

What does the color flame mean?

blue gas flame

Blue flame means that everything is OK and the air/gas mixture is in the correct ratio.

Yellow flame occurs when there is not enough air coming to the flame.

Orange or red flame happens when dust and other debris burn together with the gas.

Note: The orange flame doesn’t always indicate a problem, as it could last for a minute or two, and as the dust settles down, or gets burned, the flame goes back to blue glow.

Preventing accidents

Most of today's gas water heaters are equipped with the FVIR or Flammable Vapor Ignition Resistant technology and unique flame-arrestor feature, which prevents the flame and burning vapors to escape the combustion chamber, risking the open fire and potentially - explosion. Those water heaters that are subjected to this problem will show discoloration on the flame arrestor, which will require you to replace the unit.

Some gas water heaters are equipped with the air shutter, which allows you to adjust the air-gas mixture for proper burning. Too much of air will cause the burner flame to lift off the burner ports and burn with the noise. On the other side, if the flame becomes starved for air, the gas combustion becomes incomplete and will result in sooting. 

The manually adjustable air shutter is usually found on the cast iron burners, while the steel burners utilize the self-adjusting air mixture.

Proper gas combustion and the burner flame

The main indicators of the proper gas combustion are the stable blue flame or blue flame with the yellow inner cones (see the picture).

Proper operation requires sufficient air supply and ventilation, and the venting and exhaust system must not be blocked or have any obstructions. Fresh air is usually delivered through the provisions on the wall (atmospheric type water heater), which must be made per codes and manufacturer's instructions.

Testing the proper draft

Correctly formed burner flame on the water heater also depends on the adequate draft in the draft hood, so regular check-up is recommended. One of the easiest ways is to use the match or candle flame, or smoke, put it close to the draft hood, and if the steady flame or smoke is drawn into the opening, the proper draft is established.

If the match flame flutters or is blown out, that means products of combustion are not going through the vent system correctly, but are escaping in the surrounding, contaminating the air. The changes are visible on the burner flame also, as the burner flame changes its color to yellow or orange and the stable pattern becomes unstable; is lazy or lifts off the ports...

The most common problems with the burner flame

Burner flame is yellow and lazy which results in smoking and sooting (carbon formation)

  • Remove the scale from the top of the gas burner.
  • The problem might be insufficient air, so you have to provide proper ventilation to the water heater.
  • If the flue or vent system is blocked, make sure to find the cause, clean the pipes and remove the blockage.
  • Proper supply of combustion air is mandatory, especially if the water heater is installed in the closed or confined area.
  • If the main burner or burner orifice is clogged, make sure to unclog them or replace the orifice.
  • If the excessive heat build-up inside the chamber, the thermal switch will trip and shut down the whole water heater. The burner flame with the yellow glow is the number-one reason for the excessive smoking and sooting of the combustion chamber, flue tubes, and gas burner. This is what affects the normal operation of the water heater, damages the unit and can harm you.

emergency plumber

Burner flame floats and lifts of ports (fluctuates)

  • The orifice on the main burner might be too big. Replace it.
  • If the venting system is blocked, clean it and make sure that air and flue passageways are free of deposits and debris.
  • If the problem is with the high gas pressure, call the utility company.
  • One possibility is water in the gas line due to pipe corrosion.
  • If the problem is with the cold or excess draft, find the cause and fix the problem.
  • If the water heater is getting too much air, this requires proper adjustment on the air shutter, to reduce the air supply.
  • Check out if the flue vent is correctly connected to the water heater? Reconnect it if necessary.
  • Check out the gas valve and if there is a problem do not try to fix it, get a new one.

Note: If you find the unstable flame in an old water heater and you are unsuccessful in identifying the problem, it might be worthwhile to get and install a new gas unit, especially if you have other gas appliance on the same line operating without problems.

Burner flame is noisy

  • Reduce the air supply on the air shutter as the water heater is getting too much air.
  • Check with the utility company as the heater might be having high gas pressure.
  • Correct the problem related to the excess draft.

Burner flame is too high

  • High gas pressure... check with the utility company.
  • Loose or no connection between the water heater and the flue.
  • If there is reduced air supply, increase the amount of air.


Sooting is caused due to incomplete burning. Soot can be recognized as the black substance consisting mainly of carbon particles, that can accumulate on the heater’s elements, affecting its normal operation or even worse affect your health. Except for the natural gas burners, the problem can also occur in propane heaters, if the incorrect components (orifice) are used or gas regulators.


Keep in mind that the adequate supply of combustion and ventilating air must be provided without any obstructions. If there is an insufficient supply of air, the products of combustion will re-circulate, which will contaminate the surrounding air and cause the health issues.

As seen from the above text, one of the first signals of the improper gas combustion is the change in flame pattern, its color, shape, and height.

Visual checking of the main burner, burner flame, and pilot light should be done regularly, at least once in six months, followed by cleaning the dust and debris on the gas burner and combustion chamber.

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