Water Heater Pilot Light Keeps Going Out: 5 Real Causes

A pilot that will not stay lit is almost always one of five things: a weak or failed thermocouple, a dirty pilot orifice, a blocked flue or air supply, a draught reaching the burner chamber, or a gas control valve at the end of its life. They are listed in the order we find them.

The thermocouple, and why it fails first

The thermocouple sits in the pilot flame and generates a tiny voltage that holds the gas valve open. It is a consumable: after years in a flame it weakens, the voltage drops below the valve's threshold, and the valve shuts as designed. The symptom is exact: the pilot lights, burns while you hold the button, and dies within seconds of releasing it.

A lazy yellow pilot means air, not gas

A healthy pilot is a crisp blue flame wrapping the thermocouple tip. Yellow, floppy or lifting off means the orifice is partly blocked or the burner chamber is not getting clean air. In a garage installation the usual culprits are lint, dust and spider webbing. Genuinely common, and genuinely a service item rather than a failure.

Draughts and combustion air

A heater in a garage near a door, or in a closet with a vent that has been blocked by storage, will blow out or starve. If the pilot goes out on windy days, or after boxes were stacked against the unit, look there before ordering parts.

When to stop and call

Two hard stops. If you smell gas at any point, leave the house, do not touch switches, and call SoCalGas from outside on 1-800-427-2200. And if the pilot lights but the main burner never comes on, or the unit lights and shuts off repeatedly, the control valve is suspect: that is a gas-carrying component and it is not a homeowner repair.

Worth knowing before you spend

A thermocouple on an eight-year-old heater is money well spent. The same part on a fifteen-year-old tank that is also rumbling and rusting at the base is postponing a decision. We will tell you which one you have before quoting either, and the price is agreed in writing first.

How often this is maintenance rather than failure

More often than most owners expect. A garage heater lives in dust, lint and spider webbing, and the pilot orifice and burner air intake are exactly where that collects. A unit that has run for years untouched and starts dropping its pilot is frequently asking to be cleaned, not replaced, which is worth knowing before anyone quotes you a new heater on the strength of one symptom.