Water Heater Flame Too High or Yellow: What It Means
On this page (6 sections)
The Short Answer: A main burner flame on a gas tank is much larger than the pilot, and that alone is normal. It is a problem if the flame is lifting off the burner and roaring, lazy and yellow with soot, or reaching out of the combustion chamber. Those point to wrong gas pressure or orifice, blocked air, or a venting problem. Turn the control to OFF and have it serviced.
Normal flame versus a problem flame
Look only through the sight glass with the outer cover in place; do not remove the inner combustion door, which is sealed on modern flammable-vapor-resistant (FVIR) tanks.
| What you see through the sight glass | Likely cause | Urgency |
|---|---|---|
| Steady blue flame sitting on the burner ports, perhaps with small orange flecks | Normal; orange specks are usually dust | None |
| Large, noisy flame lifting away from the ports | Overfiring: gas pressure too high, a failing regulator, or the wrong orifice for the gas type | Turn the heater off; service soon |
| Soft, wavy yellow flame, soot on the glass or around the top | Not enough combustion air: blocked FVIR intake screen, lint, or wrong gas conversion | Turn it off; possible carbon monoxide |
| Flame or scorch marks outside the chamber, near the burner opening | Flame rollout from a blocked flue or vent | Turn it off now and leave it off |
| Yellow, sputtering flame with water dripping or a rust trail | Water on the burner from condensation or a tank leak | See water dripping on the burner |
Why a flame runs too high
- Wrong orifice for the gas. Natural-gas and propane (LP) burners use different orifices and control settings. A heater set up for propane running on natural gas, or the reverse, will burn badly. The rating plate states which gas the heater was built or converted for.
- Gas pressure out of range. The combination gas control regulates pressure to the burner. If its regulator fails, or the supply pressure is wrong, the flame can grow. Supply and manifold pressures are listed on the rating plate and are measured only by a qualified technician.
- Restricted air. FVIR tanks draw combustion air through a screen near the floor. Lint, dust, or pet hair packing that screen starves the flame, which often makes it look tall, yellow, and unstable before the heater shuts itself off.
- Poor venting. A disconnected, blocked, or undersized vent can push hot gases back into the chamber and toward the room.
What you can check safely
- Turn the gas control to OFF using the instructions printed on the heater’s label if the flame looks abnormal or you see soot.
- Look at the bottom of the heater for lint or dust around the air intake and keep the area clear of storage, laundry, and chemicals. Ask a technician to clean a sealed intake screen.
- Check the draft hood on a standard atmospheric tank (the metal cap where the vent pipe meets the top) for soot, scorch marks, or a pipe that is no longer seated.
- Read the rating plate to see the gas type, then confirm it matches what your home uses.
- Note your symptoms: soot, burning smell, headaches when near the heater, or water hotter than usual.
What the technician will check
A gas technician measures supply and manifold pressure with a gauge, checks that the orifice and control match the gas type, inspects and cleans the burner and FVIR intake, and tests the vent for proper draft and spillage. Many will also check combustion and carbon monoxide levels. If the gas control’s regulator has failed, the control is replaced; a burner that is sooted but sound can usually be cleaned or replaced as a part. See replacing a burner assembly for what that repair involves.
Repair or replace
Most flame problems are repairable: cleaning, a correct orifice, a vent fix, or a new gas control. Replacement becomes the answer when the flame problem is caused by water from a leaking tank, or when overfiring has badly damaged the flue or combustion chamber.
Frequently Asked Questions
Q: Can I turn the flame down with the temperature dial? A: No. The temperature dial sets the water temperature and decides when the burner turns on and off. It does not change flame size. Flame size is set by the burner orifice and the gas control’s pressure regulator.
Q: Is a yellow flame on a water heater dangerous? A: A flame that stays yellow and lazy, especially with soot, is burning incompletely and can produce carbon monoxide. Turn the heater off, make sure you have working CO alarms, and have it inspected. Brief orange flickers in an otherwise blue flame are usually dust and are not a concern.
Q: Why did the flame change after a new heater or a propane conversion? A: A heater installed on the wrong gas, or a conversion kit that was not completed, will burn incorrectly. The installer should verify the orifice, control, and pressures for your gas type.
Manuals and supporting references
These links distinguish general safety information from model-specific documentation. A manual directory helps you locate your unit’s instructions; it does not establish that every model uses the same parts, codes, or test values.
- PG&E: recognizing and responding to a gas leak (opens in a new tab)Emergency actions for suspected fuel-gas leaks.
- CPSC: carbon monoxide fact sheet (opens in a new tab)Carbon monoxide hazards and emergency response.
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