Why Is My Water Heater Pilot Light Not Staying On?
A gas water heater pilot that lights but won't stay on usually points to a faulty thermocouple. Here's what causes it and what to check before calling a pro.
When your gas water heater’s pilot light ignites but won’t stay lit, the most common culprit is a faulty thermocouple — a small safety device that senses the pilot flame and keeps the gas valve open. When it fails or is misaligned, it shuts the gas off as a safety measure, and the pilot goes out.
What causes a pilot light to keep going out?
A bad thermocouple. This metal probe sits in the pilot flame. When working, it generates a small voltage that tells the gas valve “the pilot is lit, it’s safe to keep gas flowing.” A worn, dirty, or misaligned thermocouple stops sending that signal, so the valve closes and the flame dies.
A dirty or mispositioned pilot. If the pilot flame is weak, yellow, or not wrapping around the thermocouple tip, it won’t heat the thermocouple enough. Dirt or debris in the pilot orifice can cause this.
A draft or venting issue. A strong draft can blow the pilot out, and venting problems can disrupt combustion.
A failing gas valve. Less commonly, the gas control valve itself is faulty and won’t hold the pilot.
What you can safely check
Make sure the gas is on and there’s no gas interruption, and that you’re following the lighting instructions on the heater’s label exactly. Beyond that — because this involves gas — diagnosing and replacing components is best left to a professional.
When to call a professional
If the pilot won’t stay lit after a proper relight, call a pro. A technician can test and replace the thermocouple, clean the pilot assembly, check the gas valve, and confirm safe venting. Anything involving the gas system warrants a licensed professional, both for a correct fix and for safety.
If your pilot won’t stay lit, our team can get your hot water back safely. Explore our water heater service or contact us 24/7. Note: if you ever smell gas, leave immediately and call from a safe location.
General guidance only; gas appliance repairs should be performed by a licensed professional.
Frequently asked questions
- What is a thermocouple on a water heater?
- It's a small safety sensor that sits in the pilot flame. When the pilot is lit, the thermocouple generates a tiny voltage that holds the gas valve open. If it doesn't sense a flame, it shuts the gas off so unburned gas can't escape — which is why a failing one keeps killing your pilot.
- Can I replace a water heater thermocouple myself?
- Because it's part of the gas system, we recommend leaving it to a professional. A licensed technician can replace the thermocouple, clean the pilot assembly, and check the gas valve and venting in one visit — ensuring the fix is both correct and safe, which matters any time gas is involved.
- Why does my pilot light keep going out?
- The usual culprit is a failing thermocouple or a weak, dirty pilot flame that isn't heating the thermocouple enough. Drafts, venting problems, or a faulty gas control valve can also be responsible. If the pilot won't stay lit after a proper relight following the label instructions, it's time to call a pro.