Common Causes of Pilot Light Failure
- Worn Thermocouple (Most Common) — This small safety device sits in the pilot flame and generates a tiny electrical signal that tells the gas valve "the pilot is lit, keep gas flowing." When the thermocouple wears out or gets coated in soot, it can't generate a strong enough signal, so the gas valve shuts off gas flow—even though the pilot is technically burning fine. This causes the pilot to "go out" repeatedly.
- Dirty or Clogged Pilot Orifice — Dust, soot, or debris can clog the small opening that the pilot gas flows through, causing a weak or unstable flame that's easily extinguished.
- Draft Blowing Out the Flame — Air currents from nearby vents, doors, or ventilation can blow out an otherwise healthy pilot flame.
- Failing Gas Valve — Less common, but if the thermocouple and pilot assembly test fine, the gas valve itself may be failing to maintain consistent gas flow.
- Air in the Gas Line — After work on the gas system or a new tank installation, air trapped in the line can cause initial pilot lighting issues that resolve once fully purged.
Safe Homeowner Diagnostic Checks
- Follow the manufacturer's relighting instructions printed on the water heater's control panel or door.
- Hold the pilot button down for the full recommended time (usually 30-60 seconds) after lighting to allow the thermocouple to heat up sufficiently.
- Observe the pilot flame color — it should be a steady blue flame. A yellow, flickering flame indicates a combustion issue.
- Check for drafts near the unit that could be blowing out the pilot.
- Note how long the pilot stays lit before going out — seconds vs. hours helps us diagnose the specific cause before we arrive.
When to Call a Professional
- The pilot won't stay lit after 2-3 relighting attempts following manufacturer instructions
- You smell gas at any point — stop immediately, shut off the gas supply, and call
- The pilot flame looks yellow or unstable rather than steady blue
- The pilot lights but the burner doesn't ignite
- Your unit is older than 10 years and having other issues along with the pilot problem
Cost Context for Pilot Light Repairs
| Repair Type | Typical Cost Range |
|---|---|
| Thermocouple replacement | $150 – $250 |
| Pilot assembly & orifice cleaning | $150 – $220 |
| Gas valve replacement | $300 – $450 |
Pilot Light Won't Stay Lit FAQs
The most common cause by far is a failed or worn thermocouple—the safety sensor that detects whether the pilot flame is burning. When it wears out, it signals the gas valve to shut off gas flow even when the pilot is actually lit. Other causes include a dirty pilot orifice, a draft blowing out the flame, or a failing gas valve.
Yes, most manufacturers print step-by-step relighting instructions directly on the water heater. If you can successfully relight it and it stays lit, no further action needed. If it goes out again within minutes to hours, that points to a thermocouple failure requiring replacement.
Thermocouple replacement in Nampa typically costs $150–$250, including parts and labor. It's one of the most common and most affordable gas water heater repairs.
Call a licensed plumber or dedicated water heater service company. Nampa Water Heater Pros specializes exclusively in water heater repair, installation, and replacement—giving faster, more accurate diagnosis than a general plumber.