Short answer: If you smell gas, leave the house and call the gas company before anything else. Otherwise, make sure the gas valve is open and relight the pilot exactly as the label on the heater says. Bob Vila explains that if the pilot lights but goes out as soon as you release the control knob, the thermocouple is the usual suspect: its tip must sit in the pilot flame. A yellow flame instead of blue, or a pilot in a sealed burner chamber, is a job for a plumber.
Quick diagnosis
| What you notice | Most likely cause | What to check | Call a pro? |
|---|---|---|---|
| Pilot will not light at all, no gas sound | Gas valve closed or no gas supply | Check the valve and other gas appliances | If gas is on |
| Lights, goes out when you let go of the knob | Thermocouple misaligned or failing | Check that its tip sits in the flame | Often |
| Pilot keeps blowing out | Draft from a vent, door or fan | Look for drafts around the heater | If it continues |
| Yellow or lazy pilot flame | Gas-air mix problem, possible carbon monoxide | Ventilate; do not keep relighting | Yes |
| Sealed burner (no access to pilot) | Newer flammable-vapor design | Do not force it | Yes |
| Smell of gas | Gas leak | Leave the house now | Gas company |
Safety first
- If you smell gas (rotten eggs), leave the house, do not use switches or phones inside, and call the gas company from outside.
- Bob Vila warns that a yellow flame can signal carbon monoxide; if anyone feels dizzy, faint or nauseated, get to fresh air and seek medical help.
- Make sure your carbon monoxide alarms work.
Relight it the right way
- Find the lighting instructions on the label on the heater; follow them exactly for your model.
- Turn the control to Off and wait the time on the label (usually several minutes) for gas to clear.
- Turn to Pilot, hold the knob down and press the igniter (or light it as the label says).
- Keep holding the knob for the time on the label, then release slowly and turn to On.
If it goes out when you release the knob
The thermocouple (or thermopile) senses the pilot flame and keeps the gas valve open. If its tip is not in the flame, or it has worn out, the valve closes and the pilot dies. Bob Vila notes it can be adjusted or replaced; if you are not comfortable working near a gas valve, call a plumber.
Check the gas supply
Confirm the gas valve on the line to the heater is open and look for a kinked flexible line. If other gas appliances also do not work, call the gas company to check service.
When to call a professional
- You smell gas, or the pilot flame is yellow.
- The burner is in a sealed chamber you cannot reach.
- The valve is open but no gas reaches the pilot.
- The pilot keeps going out after a new thermocouple.
What it usually costs
HomeGuide (2026) lists most standard tank water heater repairs at about $150 to $700, with plumbers charging about $45 to $150 per hour plus a possible $50 to $200 call-out fee.
Frequently asked questions
Why does my water heater pilot light keep going out?
Common reasons are a bad or misaligned thermocouple, a draft, a dirty pilot, or a gas supply problem.
Is it safe to relight a water heater pilot light?
Yes, if you follow the label and there is no gas smell. If you smell gas, leave and call the gas company.
Related problems
- No hot water
- Water heater making noise
- Water heater leaking
- Hot water smells like rotten eggs
- Smell gas in the house (gas leak)
Sources
This guide is general information, not a substitute for an inspection by a licensed professional. See our disclaimer.