Water Heater Burning Smell: Causes and What to Do
On this page (6 sections)
The Short Answer: A faint oily or dusty smell during a new heater’s first heat-up, or the first run after months off, usually fades within a cycle or two. A hot-plastic or electrical smell points to overheated wiring, a thermostat, or a breaker. Soot or exhaust smells point to combustion trouble. For either, turn the heater off and have it inspected. If you smell gas, leave.
Identify the smell
| Smell | Where | Likely source | What to do |
|---|---|---|---|
| Rotten eggs or sulfur in the air | Around the heater | Possible gas leak | Leave now; call the utility or 911 from outside |
| Faint dust or oil, first heat-up | Near the burner or flue | Manufacturing oils or dust burning off | Ventilate; it should fade quickly |
| Hot plastic, burnt wiring, sharp electrical smell | Electric heater or the panel | Overheated wire connection, thermostat, or breaker | Turn the breaker off; electrician or technician |
| Exhaust, soot, or a stinging smell | Gas heater, draft hood area | Poor venting or incomplete combustion | Turn the gas control off; check CO alarms; service |
| Burning dust after a loud whoosh at startup | Gas heater burner area | Delayed ignition | Turn it off; service |
| Rotten eggs only in hot tap water | Faucets | Bacteria reacting with the anode, not burning | See hot water heater smells fishy and the smells hub |
Electric heaters: where the heat damage happens
On an electric tank, a burning smell almost always comes from a connection carrying current that has become loose or corroded. The common places are the wire terminals on the upper thermostat, the junction box on top of the heater, and the breaker in the panel. A loose connection heats up each time the heater runs, and over time it browns or melts the thermostat’s plastic. Water leaking into the element compartment speeds up the damage. A breaker that is hot or discolored is covered in water heater breaker getting hot, and burnt thermostats in what causes a water heater thermostat to burn up.
Gas heaters: combustion and venting smells
On a gas tank, the smells that matter are exhaust and soot. They mean flue gas isn’t leaving through the vent properly, or the burner isn’t burning cleanly. Causes include a blocked or disconnected vent, a dirty burner or flame arrestor, or delayed ignition, where gas builds up before it lights. Signs of this are scorch marks at the burner door, soot on top of the heater, or a flame that looks yellow and lazy instead of blue. These are carbon monoxide risks. If the smell appears only when the burner starts, see smell gas when water heater turns on.
What you can do safely
- Decide whether the smell could be gas. If there is any doubt, leave and call from outside.
- For an electric heater, switch off its breaker. For a gas heater, turn the control to OFF.
- Ventilate the room.
- Without removing any covers, look for scorched paint, melted plastic, soot, or water around the heater.
- Check that the CO alarms in the home work.
- Note when the smell happens: constantly, only while heating, or only at burner start.
If the heater is brand new and the only smell is a faint oily odor on the first heat-up, ventilate and watch it. If it continues past the first day or becomes a plastic or exhaust smell, turn the heater off and call the installer.
What the technician will check
On an electric heater, the technician isolates the power and inspects the junction box, thermostat terminals, elements, and wiring for heat damage, then replaces burnt parts and fixes the loose connection that caused the damage. On a gas heater, they check venting and draft, burner condition, the flame arrestor, ignition timing, and carbon monoxide levels around the heater.
Frequently Asked Questions
Q: Can I keep using the heater if the smell went away? A: If it was a brief burn-off on a new heater, usually yes. If it was hot plastic, electrical, or exhaust, have it inspected even if the smell has faded. These problems tend to come back and get worse.
Q: The smell started after the heater got wet. Is that related? A: Possibly. Water in an electrical compartment or the burner area can cause both damage and odors. Keep the heater off and see gas water heater got wet or have the electrical side checked.
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.
- A. O. Smith: standard electric no-hot-water diagnostic chart (opens in a new tab)Professional diagnostic context for standard electric storage heaters; not instructions to open or test your appliance.
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