Water Heater Gas Leak: Signs, Causes and What to Do
Quick answer: If you smell rotten eggs or hear hissing near a gas water heater, leave the house now. Do not flip switches, use a phone or start a car near the house. Once you are well away, call 911 and your gas utility. Most water heater gas leaks start at the flexible gas connector, a threaded joint or union, the shutoff valve or the heater’s gas control valve. Finding and fixing them is a job for the gas utility or a licensed plumber or gas fitter, not a DIY repair.
Do not try to find the leak yourself. Do not tighten fittings, move the water heater or look for the source with a flame or a flashlight you switch on in the room. Leave doors open as you go out, and stay out until the gas company or fire department says it is safe.
In this guide
Signs your water heater is leaking gas
- A rotten-egg smell near the heater, the gas line or the shutoff valve. Utilities add this odorant so leaks can be noticed.
- A hissing or whistling sound from the gas line or the control valve.
- The smell gets stronger near the heater or when the burner is trying to light.
- A gas bill that jumps with no change in how you use gas.
- Feeling dizzy, nauseous or headachy, or eye and throat irritation near the heater. Get to fresh air at once; these can also be signs of carbon monoxide from a venting problem.
If a carbon monoxide alarm goes off, leave and call 911. That is usually a venting or combustion problem rather than a gas line leak, and it is just as urgent.
A brief whiff at ignition, or a real leak?
Some people notice a very brief whiff of gas right as the burner lights. A smell that lingers, gets stronger, or is there when the burner is off is not normal. If you are not sure which you have, treat it as a leak: leave and call your gas utility. They would rather check a false alarm than miss a real leak.
On propane: propane is heavier than air and collects near the floor, in basements and in low spots, so the smell may be strongest low down. Leave the same way and call your propane supplier or 911 from outside.
The smell can fade. People get used to an odor after a while, and the odorant in gas can weaken in some situations. Do not rely on your nose alone; a natural gas or propane detector (and a carbon monoxide alarm) gives an earlier warning.
Where water heater gas leaks usually start
These are the usual leak points. The table is to help you understand what the technician finds; every repair in it is professional work.
| Leak point | Why it leaks | Usual repair |
|---|---|---|
| Flexible gas connector | Corrosion, kinks, damage, or an old uncoated brass connector | Replace the connector |
| Threaded joints and unions on the gas line | Loosened by vibration or age, or poor sealing at installation | Reseal or remake the joint |
| Gas shutoff valve | Worn stem packing, often on old valves that are rarely turned | Replace the valve |
| Gas control valve on the heater | Internal seals wear out with age | Replace the gas control valve |
| Pilot and burner tube fittings | Small brass fittings loosen or crack, often after earlier service | Refit or replace the tubing |
Old brass connectors: the U.S. Consumer Product Safety Commission has warned that older uncoated brass flexible gas connectors can fail at their soldered joints. It advises replacing any uncoated brass connector with a coated or stainless-steel one, and warns homeowners not to move an appliance to inspect the connector themselves, because even a small movement can make a weakened connector break. See the CPSC connector warning.
What happens when the gas company or a plumber arrives
- They check the area with a gas detector and shut off gas to the heater or the house if needed.
- They pinpoint the leak, usually with a detector or a leak-detection solution applied while the gas is still on, since a leak only shows while gas is flowing.
- A licensed plumber or gas fitter repairs or replaces the faulty part. Many areas require a licensed professional, and sometimes a permit, for gas work.
- They test the repaired joints, restore gas and relight the heater using the manufacturer’s instructions.
- A good technician also checks the vent and combustion, because a heater that has been leaking gas may have other problems.
Preventing gas leaks
- Have a qualified technician check the gas connections, venting and burner as your heater’s manual recommends, and whenever you notice a smell or a change in how it lights.
- Replace any old uncoated brass gas connector, but have a professional do it and do not move the heater to look.
- Keep the area around the heater clear, and never store gasoline, paint thinner or other flammables near a gas appliance.
- Fit a natural gas or propane detector and a carbon monoxide alarm, and test them as their instructions say.
Rotten-egg smell only from the hot water?
If the smell comes from the water at the hot taps rather than from the air around the heater, it is usually not a gas leak. Sulfur or sulfur-reducing bacteria in the water can react with the tank’s anode rod and make hydrogen sulfide, which smells like rotten eggs. A plumber can change the anode rod type or treat the tank; see water heater smells like rotten eggs. If you are not sure which smell it is, treat it as a gas leak and leave.
For any gas smell, call your gas utility or 911 from outside first. For repairs, use a licensed plumber or gas fitter. Suggest a guide or report a correction.
Frequently asked questions
How do I know if my water heater is leaking gas?
The main signs are a rotten-egg smell or a hissing sound near the heater or its gas line. If you notice either, leave the house and call your gas utility or 911 from outside. They have detectors that confirm a leak safely.
Is it safe to stay in my home if my water heater is leaking gas?
No. Leave immediately without using switches, appliances or phones inside, leave doors open as you go, and call 911 and your gas utility once you are away from the smell. Return only when the gas company or fire department says it is safe.
Can I fix a gas leak on my water heater myself?
No. Gas connections, connectors and valves should be repaired by a licensed plumber or gas fitter, and many areas require it by law. A mistake can cause a fire, an explosion or carbon monoxide poisoning.
Should I turn off the gas to the water heater?
If the smell is strong, do not stay to turn valves; leave and call for help. The gas company or fire department will shut off the gas. If the smell is faint and your heater’s shutoff valve is right next to you and easy to reach, the utility may tell you to close it while you wait outside. Follow what they say on the phone.
What should happen after a gas leak is repaired?
The technician should leak-test every joint they worked on with the gas on, relight the heater and check that it vents properly. Make sure you have a working carbon monoxide alarm near the heater and outside sleeping areas.
Can a gas leak happen without a strong smell?
Yes. Small leaks may give only a faint smell, people get used to an odor, and the odorant can weaken in some situations. A gas detector gives an extra warning. If you notice any gas smell at all, leave and call your utility.
Can an electric water heater leak gas?
No. An electric water heater does not use gas. If you smell gas near one, the source is another gas appliance or line nearby, so leave and call your gas utility the same way.
How often should a gas water heater be checked?
Follow the maintenance schedule in your heater’s manual, and have a qualified technician look at it straight away if you notice a gas smell, a change in the flame or trouble lighting.
Why does my water heater smell like rotten eggs?
If the smell is in the air around the heater, treat it as a gas leak and leave. If it only comes from the hot water at the taps, it is usually hydrogen sulfide from sulfur or bacteria reacting with the anode rod, which a plumber can fix.
Can a very small gas leak make you sick?
It can. In a closed room, leaking gas can cause headaches, dizziness or nausea, and the same symptoms can come from carbon monoxide if the heater is not venting properly. Even a small leak is also a fire risk. If you smell gas or anyone feels unwell near the heater, get everyone outside and call your gas utility or 911 from there.
Related: Water heater not heating · Water under your water heater · Water heater leaking from top
Sources: Pennsylvania PUC: gas emergencies · CPSC: flexible gas connectors · CPSC: carbon monoxide
Updated October 22, 2026. Written and edited by Jordan Hale. General safety guidance; for any gas smell, contact your gas utility.
