You turn on the hot water and nothing happens. You check the water heater and — sure enough — the pilot light is out again. If your water heater pilot light keeps going out, you’re not alone. It’s one of the most common gas water heater problems homeowners deal with, and in many cases, the fix is straightforward.
Here’s what’s usually going on and what you can safely check before calling a plumber.
Why Your Water Heater Pilot Light Won’t Stay Lit
The pilot light is a small flame that stays lit continuously on gas water heaters. When you turn on a hot water tap, the pilot light ignites the main burner to heat the water. If that pilot flame won’t stay lit, you’ve got no hot water — and there’s almost always a reason.
The good news: most pilot light problems come down to a handful of causes, and a few of them are things you can check yourself.
5 Common Causes (and What You Can Do)
1. Dirty or Failing Thermocouple
This is the most common reason a water heater pilot light keeps going out. The thermocouple is a small metal sensor that sits in the pilot flame. Its job is to detect whether the pilot is lit. When it senses heat, it signals the gas valve to stay open. When it doesn’t sense heat — even if the pilot is actually burning — the gas valve shuts off as a safety measure.
Over time, the thermocouple can get coated with soot or corrosion, bending it away from the flame or reducing its sensitivity.
What you can try: Turn off the gas and let everything cool down. Gently clean the thermocouple tip with fine-grit sandpaper. Make sure it’s positioned so the pilot flame directly contacts the tip. Relight and see if it holds.
If cleaning doesn’t help, the thermocouple may need to be replaced. It’s an inexpensive part, but if you’re not experienced working around gas lines, this is a good time to call a plumber.
2. Dirty Pilot Tube
The pilot tube is the small supply line that feeds gas to the pilot light. If it gets partially clogged with dust or debris, the gas flow weakens and the pilot flame becomes too small to heat the thermocouple properly. The result: the thermocouple thinks the pilot is out and shuts off the gas.
What you can try: With the gas off and things cooled down, you can try gently clearing the pilot tube opening with a needle or a blast of compressed air. Be careful not to damage the opening.
3. Drafts or Ventilation Problems
A strong draft can blow out the pilot light, especially if your water heater is near a window, an exterior door, or a return air vent. Downdrafts through the flue (the exhaust vent on top of the water heater) can also snuff out the flame.
What you can check: Pay attention to when the pilot goes out. Is it always windy? Does it happen when the HVAC kicks on? If you notice a pattern, the fix might be as simple as sealing a gap or redirecting airflow. If the problem is the flue itself, a plumber or HVAC tech should take a look — flue issues can also be a carbon monoxide concern.
4. Faulty Gas Control Valve
The gas control valve regulates gas flow to both the pilot and the main burner. If it’s malfunctioning, it may not keep enough gas flowing to the pilot. Symptoms include difficulty lighting the pilot at all, or the pilot lighting but going out the moment you release the control knob.
What you can do: Not much, unfortunately. A faulty gas valve isn’t a DIY repair — it needs to be diagnosed and replaced by a licensed plumber.
5. Flex Line or Gas Supply Issues
A kinked or partially blocked flex line (the corrugated connector between your gas supply and the water heater) can restrict gas flow. Low gas pressure from the utility can cause similar symptoms.
What to check: Look at the flex line for obvious kinks or damage. If your gas stove and other gas appliances are also acting up, the issue may be on the supply side — contact your gas company.
How to Safely Relight Your Water Heater Pilot Light
If the pilot is out and you want to try relighting it, here’s the general process. Always check your specific unit’s manual for exact instructions, since steps vary by model.
- Turn the gas control knob to “Off” and wait at least five minutes for any residual gas to clear.
- If you smell gas at any point — stop. Don’t light anything. Leave the area and call your gas company immediately.
- Turn the knob to “Pilot.” Press and hold the knob down (or press the separate pilot button, depending on your model).
- While holding the knob, light the pilot using the built-in igniter or a long lighter.
- Keep holding the knob for 30 to 60 seconds after the pilot lights. This gives the thermocouple time to heat up and signal the gas valve to stay open.
- Release the knob slowly. If the pilot stays lit, turn the gas control to “On” and set your desired temperature.
If the pilot goes out immediately after you release the knob, the thermocouple is the most likely culprit.
When It’s Time to Call a Plumber
Some pilot light issues are quick fixes. Others are signs of a bigger problem. Call a licensed plumber if:
- The pilot won’t stay lit after cleaning the thermocouple and pilot tube. There may be a gas valve or venting issue that needs professional diagnosis.
- You smell gas. This is never something to troubleshoot yourself. Leave and call 911 or your gas company.
- Your water heater is more than 10 years old. Repeated pilot problems on an aging unit often mean it’s nearing the end of its useful life. A plumber can tell you whether repair or replacement makes more sense. Watch for other signs your water heater is about to fail.
- You’re not comfortable working around gas appliances. That’s completely reasonable. Gas work isn’t something to guess at.
Should You Repair or Replace?
If your pilot light keeps going out and the water heater is relatively new (under 8 years), a repair — usually a thermocouple or gas valve replacement — is typically the right call.
But if the unit is 10 to 12 years old and you’ve been chasing multiple issues, replacement may save you money in the long run. Newer models are more energy-efficient and come with updated safety features. If you’re weighing your options, check out what’s involved with water heater installation and what water heater installation costs in Los Angeles.
Regular water heater maintenance — like annual flushing and periodic thermocouple checks — can extend the life of your unit and prevent many of the problems that cause pilot light failures in the first place.
And while you’re inspecting things, it’s worth knowing about the hidden cost of ignoring a leaky water heater relief valve — another common issue that’s easy to overlook until it becomes expensive.
The Bottom Line
A water heater pilot light that keeps going out is annoying, but it’s usually fixable. Start with the thermocouple — that’s the cause more often than not. If basic troubleshooting doesn’t solve it, or if anything about the situation feels unsafe, don’t push it.
If your pilot light keeps going out or you’re not comfortable troubleshooting a gas appliance, call Western Rooter & Plumbing at (626) 448-6455 or schedule service online through our website.
