Why a pilot goes out
On a standing-pilot gas tank, a small flame burns all the time and lights the main burner when the thermostat calls for heat. A sensor sitting in that flame, usually a thermocouple, tells the gas valve the pilot is lit. If the sensor stops reporting heat, the valve shuts off gas to protect the house.
So when a pilot lights while you hold the button and dies when you let go, the gas valve is not getting the signal it needs. The flame may be too weak to heat the sensor, the sensor may be worn, or the valve may be failing.
Likely causes
| Cause | What it looks like | Who handles it |
|---|---|---|
| Worn or misaligned thermocouple | Pilot lights, then goes out when the button is released | Licensed plumber |
| Dirty or clogged pilot orifice | Small, weak or yellow pilot flame | Licensed plumber |
| Draft or poor combustion air | Pilot blows out, especially when doors open | Licensed plumber; check the space too |
| Failing gas control valve | No pilot gas, or repeated failures after part swaps | Licensed plumber |
| Tripped thermal cutoff on newer sealed designs | Will not relight after an overheating event | Licensed plumber |
What you can reasonably do
- Read the label.Most gas tanks have lighting instructions on the jacket. Follow them exactly, once.
- Check the dial.Make sure the control is not set to Off or Vacation, and that the gas shutoff on the supply line is open.
- Look at the space.Garage doors, fans or clutter near the burner opening can disturb the flame and starve it of air. Clear the area around the base.
- Stop after one failed attempt.If the pilot will not stay lit, leave the control off and call a licensed plumber rather than trying again and again.
Tell the plumber
- Whether the pilot lights at all, or lights and goes out
- Color and size of the flame if you saw it
- Whether other gas appliances are working
- Brand, model and manufacture date from the rating plate
- Anything stored near the heater, especially paint, fuel or solvents
Common questions
- Is a thermocouple replacement a big job?
- It is usually a small part, but it is gas work on a combustion appliance. A licensed plumber should do it and check the flame and venting afterward.
- Why does my pilot go out when the garage door opens?
- A strong draft can blow out or weaken the pilot. That is worth mentioning to the plumber, who can check combustion air and the burner area.
- Should I store things next to the water heater?
- Keep the area around a gas heater clear, and never store gasoline, paint thinner or other flammable liquids near it.
General information for Fullerton, not a quote or professional advice. In an emergency, call 911.