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Fix a water heater pilot that will not stay lit

We'll confirm the pilot lights but goes out, rule out draft and gas supply, then replace the thermocouple or tell you when to call a pro.

Troubleshooting · Home plumbing
15–45 min
What you'll need
  • Long lighter or match
  • Multimeter (for continuity test)
  • Replacement thermocouple (if tests show a fault)
  • Adjustable wrench
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Steps

Goal: Confirm the pilot lights but goes out, rule out draft and gas, then isolate the thermocouple or call a pro.

  • Turn the gas control knob to Pilot, press and hold, light the pilot with a long lighter, hold for 60 seconds, then release slowly.
  • Good: The pilot lights but goes out when you release—thermocouple or gas valve. Proceed to Check draft and gas.
  • Bad: The pilot does not light at all—different problem (gas supply, pilot orifice). See When to get help.

Check draft and gas

Goal: Rule out draft and gas supply before replacing parts.

  • Check for draft from vents, windows, or doors. Block obvious drafts and retry.
  • Confirm the main gas shutoff and any local shutoff are fully open (parallel to the pipe).
  • Good: No draft, gas on. Proceed to Replace thermocouple.
  • Bad: Draft present or gas off—fix those first, then retry.

Replace thermocouple

Goal: Inspect, test, and replace the thermocouple if faulty.

  • Inspect the thermocouple—the thin metal probe next to the pilot. The tip must sit in the flame. If bent away, gently bend it into the flame.
  • Shut off the gas. Disconnect the thermocouple from the gas valve. Test for continuity with a multimeter. No continuity means replace.
  • Buy a matching thermocouple (check the part number). Install it, route it the same way, reconnect to the gas valve. Light the pilot and hold for 60 seconds.
  • Good: The pilot stays lit when you release the knob.
  • Bad: The pilot still goes out—call a pro. Gas valve may be faulty.

When to get help

If you smell gas, evacuate immediately. Do not turn on lights or appliances. Call 911 or your gas utility from outside. Do not call a technician for an active gas leak.

Call a plumber or HVAC technician if:

  • The pilot does not light at all.
  • The pilot still goes out after replacing the thermocouple.
  • You suspect low gas pressure.
  • You are not comfortable working with gas appliances.

Verification

  • The pilot flame stays lit when you release the gas control knob.
  • The pilot flame is blue and strong.
  • Hot water is available at the fixtures.

Escalation ladder

Work from the device outward. Stop when the problem is fixed.

  1. Confirm symptom Verify the pilot lights but goes out when you release the knob.
  2. Draft and gas Check for draft and confirm gas supply is on.
  3. Thermocouple position Confirm the thermocouple tip sits in the pilot flame.
  4. Replace thermocouple Test and replace the thermocouple if faulty.
  5. Call a pro Gas smell—evacuate, call 911 or gas utility. Pilot still goes out after replacement—call a plumber or HVAC technician.

What to capture if you need help

Before calling support or posting for help, have these ready. It speeds everything up.

  • Whether the pilot lights at all
  • Whether draft is present
  • Thermocouple test results
  • Steps already tried

Does the pilot light but go out when you release the knob?

Turn the gas control to Pilot, press and hold, light the pilot, hold 60 seconds, then release. If it goes out when you release, the thermocouple or gas valve is likely at fault.

Turn the gas control knob to Pilot, press and hold, light the pilot with a long lighter, hold for 60 seconds, then release slowly. Good: pilot lights but goes out when released—thermocouple or gas valve. Bad: pilot does not light at all—different problem (gas supply, pilot orifice).

Yes No

You can change your answer later.

Is there draft or is the gas supply off?

Draft can blow out the pilot. Gas supply must be fully on.

Check for draft from vents, windows, or doors. Check the gas shutoff valves—main and local—are fully open (parallel to pipe). Good: no draft, gas on. Bad: draft present or gas off—fix those first.

Yes No

You can change your answer later.

Fix draft or gas, then retry

Block drafts, open gas valves fully. Retry lighting the pilot. If it stays lit, the problem was draft or gas. If it still goes out, proceed to thermocouple.

Done

Is the thermocouple tip in the pilot flame?

The thermocouple must sit in the flame tip to keep the gas valve open.

Inspect the thermocouple—a thin metal probe next to the pilot. The tip must sit in the flame. If bent away, gently bend it into the flame. Retry. Good: tip in flame, pilot stays lit. Bad: still goes out—test or replace thermocouple.

Yes No

You can change your answer later.

Reposition thermocouple and retry

Gently bend the thermocouple so the tip sits in the center of the pilot flame. Light the pilot and hold 60 seconds. If it stays lit, the problem was position. If not, test or replace.

Done

Does the thermocouple have continuity?

Shut off gas. Disconnect thermocouple. Test with multimeter.

Shut off gas. Disconnect the thermocouple from the gas valve. Test for continuity with a multimeter. No continuity or very high resistance means replace. Good: continuity—check pilot orifice. Bad: no continuity—replace thermocouple.

Yes No

You can change your answer later.

Replace thermocouple and test

Replace the thermocouple with a matching part. Reconnect, light the pilot, hold 60 seconds. The pilot should stay lit. If it still goes out, call a pro—gas valve may be faulty.

Done

Is the pilot flame weak or yellow?

A weak flame may not heat the thermocouple enough.

Check the pilot flame. It should be blue and strong. If weak or yellow, clean the pilot orifice with a thin wire—do not enlarge it. Light the pilot. If the flame is still weak, replace the pilot assembly or call a pro.

Yes No

You can change your answer later.

Clean pilot orifice and retry

Shut off gas. Clean the pilot orifice with a thin wire or orifice tool. Do not enlarge it. Reassemble and light the pilot. The flame should be blue and strong. If the pilot still goes out, call a pro.

Done

Call a pro

If you smell gas, evacuate immediately. Call 911 or your gas utility from outside. Call a plumber or HVAC technician if: the pilot does not light at all; the pilot still goes out after replacing the thermocouple; you suspect low gas pressure; or you are not comfortable with gas.

Done

Reviewed by Blackbox Atlas

Frequently asked questions

Why would a water heater pilot not stay lit?
The thermocouple is the most common cause—it senses the pilot flame and keeps the gas valve open. A bent, corroded, or failed thermocouple will shut off gas when you release the knob. Draft, low gas pressure, or a dirty pilot orifice can also cause the pilot to go out.
Can I replace the thermocouple myself?
Yes. Shut off the gas, disconnect the thermocouple from the gas valve, remove the pilot assembly, and install a matching replacement. If you are not comfortable with gas appliances, call a plumber or HVAC technician.
When should I call a pro for a pilot that will not stay lit?
If you smell gas, evacuate and call 911 or your gas utility from outside. Call a plumber or HVAC technician if the pilot still goes out after replacing the thermocouple, if gas pressure seems low, or if you are not comfortable working with gas.

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