If your water heater pilot light won’t stay lit, the most common cause is a faulty thermocouple, followed by a dirty pilot or gas supply issue.
Quick Answer
Start Here: What’s Happening?
Pilot Light Diagnostic Table
Common Causes
Thermocouple Problems
Dirty or Blocked Pilot
Gas Supply Issues
How to Fix It
When to Call a Pro
Next Steps & Related Guides
FAQs
If your water heater pilot lights but won’t stay lit, the system is shutting off gas as a safety measure. The key is to identify what’s preventing the pilot from staying stable.
Quick Answer
A pilot light that won’t stay lit is most often caused by a bad thermocouple, a dirty pilot opening, or an issue with the gas supply or control valve.
Start Here: What’s Happening?
- Pilot lights, then goes out immediately: Thermocouple problem
- Pilot won’t light at all: Gas supply or ignition issue
- Pilot flame is weak or flickering: Dirty pilot or airflow issue
Pilot Light Diagnostic Table
| What you notice | Likely cause | What to check |
|---|---|---|
| Pilot goes out after release | Faulty thermocouple | Replace thermocouple |
| Pilot won’t light | No gas supply | Check gas valve |
| Weak or flickering flame | Dirty pilot opening | Clean pilot |
| Pilot goes out randomly | Draft or airflow issue | Check venting |
Common Causes
Faulty thermocouple
The thermocouple detects the pilot flame and allows gas to flow. If it fails, it shuts off gas—even if the pilot is lit.
Dirty or clogged pilot opening
Dust, debris, or mineral buildup can weaken the flame and prevent proper operation.
Gas supply issue
If gas isn’t flowing properly, the pilot won’t stay lit.
Draft or airflow problem
Strong drafts or improper venting can blow out the pilot flame.
Faulty gas control valve
If the control valve fails, it may not maintain gas flow to the pilot.
Thermocouple Problems
This is the most common cause. Thermocouples wear out over time and are relatively inexpensive to replace.
Dirty or Blocked Pilot
A weak or irregular flame is often caused by a clogged pilot orifice. Cleaning it can restore proper function.
Gas Supply Issues
Make sure the gas valve is open and other gas appliances are working normally.
How to Fix It
Replace the thermocouple
Turn off the gas supply and allow the unit to cool. Remove the burner assembly, disconnect the old thermocouple, and install a matching replacement. Reassemble and relight the pilot.
Clean the pilot opening
Turn off gas and use a thin wire or needle to gently clear debris from the pilot orifice. Blow out dust with compressed air if available. A clean pilot should produce a steady blue flame.
Check gas supply and valves
Make sure the gas shutoff valve is fully open and that other gas appliances are working. If not, the issue may be with your gas supply.
Shield the unit from drafts
Check for strong air movement near the heater, especially from vents or open doors. Drafts can blow out the pilot flame. Adjust airflow or add shielding if needed.
When to Call a Pro
- You smell gas
- Pilot won’t stay lit after replacing thermocouple
- The DIY steps given above are beyond your abilities
- Gas control valve may be faulty
- You are unsure how to safely relight the pilot
Next Steps & Related Guides
FAQs
Why does my pilot light go out when I release the button?
This is almost always caused by a faulty thermocouple.
Can I replace a thermocouple myself?
Yes, but follow safety instructions and turn off gas before working.
Why is my pilot flame weak?
A dirty pilot opening or airflow issue is usually the cause.
Is it dangerous if the pilot won’t stay lit?
It can be, especially if gas is leaking or controls are faulty—use caution.
