Water Heater Pilot Light Won't Stay Lit? Causes & Fixes

The most likely cause: a failing thermocouple

The thermocouple is a small copper rod that sits in the pilot flame. It generates a tiny electrical signal that tells the gas valve "the pilot is lit, keep gas flowing." When the thermocouple weakens, the gas valve shuts off as a safety measure and your pilot goes out.

Signs it is the thermocouple:

• Pilot lights but goes out seconds after you release the pilot button
• Pilot stays lit for a few minutes then dies
• Pilot repeatedly relights then fails
• The unit is 5+ years old

The fix: thermocouple replacement. $145-$220 installed, about 45 minutes of work.

Other reasons a pilot won't stay lit

Dirty or blocked pilot tube

Dust and debris can clog the pilot tube, creating a weak flame that cannot heat the thermocouple. Professional cleaning usually solves this.

Gas supply issues

Low gas pressure, a kinked supply line, or a failing regulator can starve the pilot. If other gas appliances have been acting up, this may be the cause.

Draft problems

Strong drafts from vents, HVAC returns, or open windows blow the pilot out.

Failed gas control valve

Less common but it happens. When the valve itself is the problem, no thermocouple replacement will fix it. We diagnose with a millivolt test.

Flammable vapor sensor (FVIR)

Modern gas water heaters have an FVIR shutdown. If tripped by gasoline, paint fumes, or other vapors, the pilot won't stay lit until reset.

Safe DIY steps

• Follow the lighting instructions exactly on the unit's label
• Check for obvious obstructions near the pilot tube
• Verify the gas supply is fully on
• Check thermostat setting and any reset buttons

Do NOT attempt to replace the thermocouple yourself unless comfortable with gas work, adjust the gas valve or regulator, or keep lighting the pilot repeatedly if it won't stay lit (gas can accumulate).

When to call

• You smell gas near the unit
• The pilot won't light at all
• You've tried 3+ times with no success
• The unit is under warranty

See our gas water heater repair service for same-day diagnosis.

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