Water Heater Pilot Light Won't Stay Lit? Causes & Safe Fixes
A pilot that lights then dies almost always points to the thermocouple, the safety sensor that proves the flame is burning. A pilot that will not light at all usually means a dirty orifice, a draft, or no gas. Here is how to read which it is, the safe relight steps, and the one symptom that means you stop and leave.
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Safety first: if you smell gas, see water near electrical outlets or your panel, or sewage is contacting living areas, get people clear first. For a gas smell, leave and call 911 or your gas utility's emergency line before anything on this page.
- !You smell gas at any point: stop, leave the area, and call the gas utility or 911 from outside
- !You hear a hissing sound near the gas valve or burner
- !The relight instructions call for repeated attempts and gas keeps flowing without igniting
- !Soot, scorch marks, or a yellow rolling flame instead of a crisp blue pilot
- !Water is pooling around the base of a gas-fired unit near the burner or controls
- ✓Confirm the gas is on: check the shutoff valve at the heater and whether other gas appliances work
- ✓Set the gas control dial to PILOT and follow the relight steps printed on the tank label exactly
- ✓Hold the pilot button down the full 30 to 60 seconds the label specifies before releasing, to let the thermocouple heat up
- ✓Look for drafts: a nearby door, vent, or strong cross-breeze can blow a pilot out, especially in a garage
- ✓Check the sight glass and burner area for dust or lint that may be choking the pilot, and let the unit cool before any inspection
- →The pilot lights but goes out within seconds of releasing the button, the classic failed thermocouple
- →The pilot will not light at all after you confirm gas is flowing
- →You have relit it and it keeps going out over hours or days
- →The flame is yellow or lifting rather than a steady blue, a combustion or venting problem
- →A newer sealed-combustion unit shows an error code or flashing light instead of a manual pilot
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Lights then dies: the thermocouple
If the pilot lights while you hold the button but goes out the moment you release it, the thermocouple is the prime suspect. This thin metal sensor sits in the pilot flame and generates a tiny voltage that tells the gas valve the flame is present. When it weakens with age or carbon buildup, the valve reads "no flame" and shuts the gas off as a safety measure, exactly what it is designed to do.
The fix is a thermocouple replacement, $150 – $300 installed, covered on our water heater repair cost page. Before that, two things are worth trying: hold the pilot button the full 30 to 60 seconds the label specifies (releasing early is a common mistake), and gently clean the pilot tube if it is sooty. If it still dies after a proper hold, the part has failed.
Won't light at all: orifice, gas, draft
A pilot that will not catch at all is a different list. First confirm gas is actually reaching the unit: check the shutoff at the heater, and whether the stove or furnace still works. A closed valve or an interrupted supply is the simplest cause and the easiest to miss.
If gas is flowing, the pilot orifice may be clogged with dust, lint, or spider webbing, common in garages and basements, choking the tiny flame. A draft is the other culprit: a door, a vent, or air moving through the space can blow the pilot out as fast as it lights. On newer sealed-combustion units there is no manual pilot at all; an electronic igniter or flame sensor does the job, and a failure there shows as an error code rather than a dark pilot.
The safe relight procedure
Every gas water heater prints relight steps on a label near the gas valve; follow those exactly, since details vary by model, and our step-by-step relight walkthrough covers the same sequence in detail. The general sequence: turn the gas control dial to OFF and wait several minutes for any gas to clear (this is the step you never rush). If you smell gas during that wait, stop here, leave, and call from outside.
With the area clear of gas odor, set the dial to PILOT, hold down the pilot button, and light the pilot (or press the igniter on units that have one). Keep holding the button the full 30 to 60 seconds the label specifies so the thermocouple heats and proves the flame, then release. If the pilot stays lit, turn the dial to ON and set your temperature. If it dies, the thermocouple is the likely answer.
When to stop and leave
There is one absolute rule that overrides every troubleshooting step: if you smell gas, leave. Do not relight, do not flip switches, do not stay to investigate. A pilot problem is a maintenance issue; a gas smell is a life-safety emergency, and the two require completely different responses.
A persistent gas odor near the heater, or anywhere in the house, means you leave immediately and call the gas utility or 911 from outside or a neighbor. Our gas smell in the house guide lays out exactly what to do and what not to touch. Come back to relighting the pilot only after the utility has cleared the home. No hot water is an inconvenience; a gas leak is not one to gamble with.
What the fix costs
Most pilot problems are inexpensive once diagnosed. A diagnostic or service call runs $100 – $250. A thermocouple, the most common fix, is $150 – $300 installed. Cleaning a clogged orifice or correcting a draft is often just the service call. A failed gas control valve, less common, runs $300 – $600.
If the same pilot problem keeps recurring on a heater past 8 to 12 years, weigh the repairs against age. Chasing thermocouples and valves on an old tank can cost more over a year than putting that money toward a new water heater. A licensed plumber can tell you in one visit whether you are looking at a $200 part or an aging unit nearing the end of its run.
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