If your gas water heater isn’t working, the cause is usually a pilot light problem, thermocouple failure, gas supply issue, or faulty control valve.
Quick Answer
Start Here: What’s Happening?
Gas Water Heater Diagnostic Table
Common Causes
Pilot Light Problems
Thermocouple Issues
Gas Supply Problems
How to Fix It
When to Call a Pro
Next Steps & Related Guides
FAQs
Gas water heaters rely on a burner and pilot light to heat water. When something goes wrong, the issue is usually related to ignition, gas flow, or safety controls.
Quick Answer
A gas water heater that isn’t working is most often caused by a pilot light that’s out, a faulty thermocouple, a gas supply issue, or a malfunctioning gas control valve.
Start Here: What’s Happening?
- No hot water at all: Pilot light or gas supply problem
- Pilot won’t stay lit: Thermocouple failure
- Water not hot enough: Burner or thermostat issue
Gas Water Heater Diagnostic Table
| What you notice | Likely cause | What to check |
|---|---|---|
| No hot water | Pilot light out | Relight pilot |
| Pilot won’t stay lit | Bad thermocouple | Replace thermocouple |
| Weak heating | Burner issue | Inspect burner flame |
| No gas flow | Gas supply problem | Check gas valve |
Common Causes
Pilot light out
If the pilot is not lit, the burner cannot heat the water.
Thermocouple failure
The thermocouple shuts off gas if the pilot goes out. If it fails, the pilot won’t stay lit.
Gas supply issue
The gas valve may be closed or there may be a supply interruption.
Faulty gas control valve
This component regulates gas flow and temperature. Failure can stop heating entirely.
Pilot Light Problems
The pilot light is the most common failure point in gas water heaters.
Thermocouple Issues
A worn thermocouple is a frequent cause of pilot problems and is relatively inexpensive to replace.
Gas Supply Problems
Ensure the gas valve is open and the supply is functioning.
How to Fix It
- Relight the pilot light (see Pilot Light Won’t Stay Lit)
- Replace the thermocouple if the pilot won’t stay lit
- Check gas supply and valves to ensure gas is flowing
When to Call a Pro
- You smell gas
- Pilot won’t stay lit after replacement
- Gas control valve failure
To Hire a Plumber…
If the repair turns out to be more complicated than expected, you can always find a qualified plumber near you.
For hiring advice, see Trade Secrets for Hiring the Right Plumber.
Next Steps & Related Guides
FAQs
Why won’t my pilot light stay lit?
This is usually caused by a faulty thermocouple.
Can I relight the pilot myself?
Yes, but follow manufacturer instructions carefully.
