Quick answer
A gas water heater pilot that lights and goes out when you release the knob usually has a worn or dirty thermocouple, or one that is not sitting in the flame. Follow the lighting label and hold the knob 30 to 60 seconds before letting go. A yellow flame, drafts, or a tripped flammable vapor sensor on newer models are the other common causes. A valve or fitting repair runs $100–$400. If you smell gas, leave and call the gas utility. Call (888) 217-6781 to reach a plumbing company taking calls in your ZIP.
Follow the short menu, then your 5-digit ZIP. The line goes quiet for a few seconds while it connects; stay on. If it does not connect, call once more: companies taking calls change minute to minute.
Written & reviewed by Marcus ReedIICRC WRT
Reviewed November 3, 2026· Next review May 2027
On a gas water heater with a standing pilot, a pilot that lights and then goes out when you release the knob almost always means the thermocouple is not keeping the gas valve open. It is one of the most common water heater repairs, and the cause is usually that small part, not the tank.
First: Safety
If you smell gas (a rotten-egg odor) near the water heater, do not try to light anything. Leave the house, then call the gas utility from outside.
Relight It Correctly
Follow the lighting instructions on the label on the tank; they differ by model. In general, you turn the control to "Pilot," hold the knob down while you light the pilot (or press the igniter button), and keep holding for 30 to 60 seconds before releasing. Letting go too early is the most common reason a good pilot goes out.
What Usually Causes It
| What you see | Likely cause |
|---|---|
| Pilot lights, goes out as soon as you release the knob | Worn or dirty thermocouple, or it is not sitting in the flame |
| Small, yellow or flickering flame | Dirty pilot orifice, draft, low gas supply |
| Pilot goes out now and then on its own | Draft from a door or vent, dirty flame sensor area, failing thermocouple |
| Pilot will not light at all | Gas supply closed, failed igniter, clogged pilot tube |
| Burner lights and goes out after a few minutes | Venting problem or a tripped flammable vapor sensor |
Talk to a plumber about this
One call reaches a plumbing company taking calls in your ZIP.
Newer Water Heaters
Many water heaters built since 2003 have a sealed combustion chamber with a flammable vapor sensor and a thermal cutoff. If either trips, the pilot will not stay lit until the part is reset or replaced, and the cause (spilled solvent nearby, poor airflow, a blocked flame arrestor) needs to be found first.
What a Repair Costs
A valve or fitting repair on a water heater sits in the $100 to $400 range on our water heater repair page. A thermocouple is at the low end; a gas control valve is at the high end. If the tank is old and also leaking, see no hot water in the house for when replacement makes more sense.
When to Call
Call if the pilot will not stay lit after a correct relight, if the flame is yellow, or if the burner shuts off after lighting. (888) 217-6781 connects you to a plumbing company taking calls in your ZIP. Follow the short menu, enter your 5-digit ZIP and stay on while it connects; if it does not connect, call once more, because the companies taking calls change minute to minute.
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Frequently Asked Questions
Why does my water heater pilot go out when I let go of the knob?
The thermocouple is usually worn, dirty or out of the flame, so it cannot hold the gas valve open. Replacing it is one of the most common water heater repairs.
Why does my pilot light keep going out on its own?
Drafts from a nearby door or vent, a dirty pilot, or a failing thermocouple. On water heaters built since 2003, a tripped flammable vapor sensor or thermal cutoff can also shut it off.
How much does it cost to fix a water heater pilot?
A valve or fitting repair runs $100–$400. A thermocouple is at the low end and a gas control valve at the high end.
Sources
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Disclaimer: HearthDry is an independent educational resource. This article is for informational purposes only and does not constitute professional, legal, or insurance advice. Consult licensed professionals before making decisions about your property or insurance claims.