Gas Smell After Water Heater Replacement
On this page (6 sections)
The Short Answer: If you smell gas (a rotten-egg or sulfur odor in the air) after a water heater was replaced, treat it as a leak. Leave the building, don’t operate switches or the heater, and call your gas utility or 911 from outside. New connections are the most likely leak points. A brief hot-metal or oily smell on the first few burner cycles is different and fades on its own.
What to do right now
- Get everyone out. Don’t turn lights or appliances on or off, and don’t use a phone indoors.
- From outside, call the gas utility’s emergency line or 911.
- Don’t go back in until the utility or fire department says it is safe.
Gas utilities answer odor calls as emergencies, and PG&E’s gas leak guidance (opens in a new tab) is typical of what they tell customers. Don’t look for the leak yourself with soapy water or a flame while the smell is in the air.
Telling the smells apart
| What you notice | Likely source | What it means |
|---|---|---|
| Rotten eggs or sulfur in the air near the heater or elsewhere | Odorant added to natural gas and propane | Possible leak: leave and call |
| Hot paint, oil, or dust smell during the first few heating cycles | Manufacturing residue burning off the new burner and flue | Normal if it fades within a few cycles and there is no gas odor |
| Rotten-egg smell only from hot taps, room air is fine | Hydrogen sulfide made in the water by bacteria reacting with the anode | Water-quality problem, not a gas leak |
| Gas smell only when the burner lights, plus a whoosh or bang | Delayed ignition | Shut the heater off; have it serviced |
If you are not sure which you have, treat it as gas.
Why it happens after a replacement
Installing a water heater means making new gas connections: a flexible connector or new pipe, a union, a sediment trap, and the connection at the gas control. Any of these can leak if a thread wasn’t sealed or a fitting wasn’t tightened. Air left in the line can also make the first lightings rough. Clearing it is installer work, not something to do by loosening a fitting (see purging air from a gas line).
A connection that was tight at installation can also be disturbed later, for example by someone moving the heater or bumping the flex line.
What happens next
The utility will usually check for gas in the air and may shut off the supply to the heater or the meter. A licensed plumber or gas fitter then finds and repairs the leak, pressure- or leak-tests the new piping, and relights the heater. If your installer did the work, call them back. If a permit was required, the inspector will also look at the gas connection, venting, and sediment trap.
After the leak is fixed
Watch for any return of the odor, especially when the burner starts. If you smell gas when the heater turns on, see smell gas when the water heater turns on. Make sure working carbon monoxide alarms are installed near sleeping areas, since a new install can also have venting problems.
Frequently Asked Questions
Q: Is it normal for a new gas water heater to smell? A: A light hot-metal or oily smell during the first few burns is common and fades. A rotten-egg smell is not normal and should be treated as a gas leak.
Q: Can I check the new connections with soapy water myself? A: Not while you can smell gas. Leave and call the utility. After the area has been declared safe, leak testing the new connections is part of the installer’s job.
Q: My hot water smells like rotten eggs after the new heater went in. Is that gas? A: If the smell comes only from the hot water and the air around the heater is fine, it is usually hydrogen sulfide in the water, not fuel gas. See water heater smells like dead animal for sulfur and other water odors.
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.
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