Symptom guide
Water heater smells: gas, burning, sulfur, or smoke
First determine whether the odor is in the room or only in the hot water. Fuel, electrical, combustion, and water-quality smells require different responses.
Safety first: Treat a gas odor, burning insulation, smoke, soot, or a carbon-monoxide alarm as urgent. Leave the area and contact the appropriate utility or emergency service from outside.
Start here
Identify the unit before following a procedure
Photograph the rating plate, control or display, and the exact symptom. Model generations can use different controls and code meanings even when the brand name is the same.
- Choose the heater typeGas tank, electric tank, tankless, heat pump, indirect, or RV.
- Record the exact clueCode, flash count, leak location, sound, or timing.
- Use the closest guideConfirm every model-specific step against the label or manual.
Gas
16 guidesAmerican Water Heater Pilot Won't Stay Lit
An American standing-pilot that dies is a thermocouple, FVIR, or gas valve. If you smell gas, leave.
GasCarbon Monoxide From the Water Heater
A CO alarm near a gas water heater can mean a blocked vent, backdrafting, a failed power-vent blower, or overfiring. What to do right away.
GasControl Box Leaking Gas? Get Out Now
A gas smell at a water heater control valve is an emergency. Leave the building and call the gas utility from outside. What not to do.
GasDon't Purge a Water Heater Gas Line Yourself
Do not open gas fittings to release air. Learn what to do after a failed installation start and when gas odor requires immediate evacuation.
GasGas Smell After Water Heater Replacement
Mercaptan after a heater swap is a leak until a utility or licensed fitter says otherwise. Leave. Don’t sniff fittings.
NavienNavien Exhaust Smells Like Gas? Leave
Gas odor at a Navien termination is an emergency. Leave and call the gas utility from outside; do not restart the unit.
RheemRheem Pilot Light Will Not Stay Lit
A Rheem pilot that dies is a thermocouple, FVIR screen, or gas valve — not a ritual relight. If you smell gas, leave and call a pro.
RheemRheem Tankless Smells Like Gas? Leave
A gas smell at a Rheem tankless should be treated as a leak until a professional says otherwise. What to do, and which odors aren't gas.
RheemRheem Water Heater Smells Like Gas? Leave
A gas smell at a Rheem, Ruud, or Richmond water heater should be treated as a leak. What to do right away, and which smells are not fuel.
GasSmell Gas After Lighting the Water Heater?
A gas smell after lighting a water heater may be unburned fuel or a leak at the control. Why you should leave, not relight, and who to call.
GasSmell Gas When the Water Heater Turns On?
A gas smell only when the burner fires can mean a leak or delayed ignition. Why you should leave and call for help rather than keep cycling it.
GasTankless Exhaust Smells Like Gas? Leave
A gas smell at a tankless exhaust can mean unburned fuel or a leak. What to do right away, and which harmless smells are sometimes mistaken for gas.
GasWater Heater Closet Smells Like Gas? Leave
Gas odor in a heater closet is an emergency. Leave, call the utility from outside. Do not soap fittings.
GasWater Heater Vent Pipe Leaking? CO Risk
Water on a water heater vent pipe can be condensate, rain, or a failed joint. Why a leaking vent can be a carbon monoxide risk.
WhirlpoolWhirlpool Pilot Light Won't Stay Lit
A Whirlpool pilot that dies is a thermocouple, dirty orifice, or FVIR — not luck. If you smell gas, leave.
GasWhy Won't My Gas Water Heater Stay Lit?
A gas water heater that lights then dies is thermocouple, thermopile, draft, or the gas valve. If you smell gas, leave.
Electric
2 guidesElectric Water Heater Smells Like Gas?
A gas smell near an electric water heater is still an emergency: another appliance or line may be leaking. What the smell can mean and what to do.
ElectricWater Heater Element Keeps Burning Out
A water heater element that keeps failing usually points to sediment, dry firing, a grounded element, or the wrong wattage. How to find the cause.
Tankless
3 guidesAO Smith Tankless Reset Button
Most A. O. Smith tankless units reset by cycling 120 V power, not a hidden button. When one reset is safe, and when a code or gas smell means stop.
NavienNavien Tankless Water Heater Exhaust Blockage
A blocked Navien exhaust can cause a lockout, gas odor, or no heat. Check the termination from outside.
TanklessTankless Water Heater Smells Like Sulfur
Sulfur smell only in tankless hot water usually comes from well water or bacteria. A sulfur smell in the air may be a gas leak. How to tell.
RV
2 guidesGirard Tankless Reset Button: Clear a Lockout
How to clear a Girard GSWH-2 lockout with a faucet or 12 V reset, when one reset is reasonable, and which codes or smells mean stop.
RVRV Water Heater Smells Like Rotten Eggs
Rotten-egg smell only in RV hot water usually comes from the anode or stagnant water. The same smell in the air may be propane. How to tell.
Troubleshooting
7 guidesHot Water Heater Smells Fishy? Split Air vs Water
A fishy smell in the air near a heater can mean overheating wiring; fishy hot water is usually water chemistry. How to tell which you have.
TroubleshootingWater Heater Alarm Going Off? Find the Beep
A beeping water heater is usually a tankless lockout, hybrid alarm, power-vent board, or leak sensor, or a nearby smoke or CO alarm.
TroubleshootingWater Heater and Furnace Both Dead at Once
Both dead at once is a shared vent, gas meter, or circuit - not two random failures. Leave if you smell gas.
TroubleshootingWater Heater Burning Smell: Shut It Down
A burning smell from a water heater can mean scorched wiring, an overheated thermostat, hot insulation, or delayed ignition. When to shut it down.
TroubleshootingWater Heater Fan Keeps Running
Record whether a water-heater fan runs during demand, cooldown, or continuously. Burning odor and abnormal operation need prompt assessment.
TroubleshootingWater Heater Smells Like a Dead Animal?
Rotten-egg HOT water is the anode. Mercaptan in AIR is a gas leak — leave. A rodent in the FVIR is different.
TroubleshootingWhite Smoke From a Water Heater
White vapor is often steam; combustion exhaust or electrical smoke is not. Shut it down, tell steam from fire.