Pilot will not light at all
You hold the control in and try to ignite it, but you never get a steady pilot flame.
Start here: Start with gas supply, the pilot orifice, and whether the igniter is actually sparking at the pilot.
Gas water heater troubleshooting
John Wood Water Heater Pilot Won’t Stay Lit
Direct answer: If the pilot lights but dies when you release the button, the most common causes are a weak thermocouple signal, a dirty pilot flame, or venting trouble that disturbs combustion. Start with the flame and vent checks before blaming the gas control.
Most likely: Most often, the pilot flame is too small or not hitting the thermocouple squarely, or the thermocouple connection is loose or failing.
First separate whether the pilot never lights at all, lights only while you hold the button, or stays on for a few minutes and then drops out. Those patterns point to different problems. Reality check: a pilot that won’t hold is usually a small combustion or sensing problem, not a whole water-heater failure. Common wrong move: relighting over and over without checking for draft, soot, or a weak pilot flame.
Don’t start with: Don’t start by replacing the gas valve or forcing repeated relights. Gas control problems do happen, but they are not the first thing I’d bet on from this symptom alone.
If the pilot never catchesCheck gas supply, the pilot tube flame, and whether the igniter is actually lighting gas at the pilot.
If it lights but dies on button releaseFocus on thermocouple position, thermocouple connection, and vent or draft issues first.
Last reviewed: 2026-04-17
What the pilot is doing tells you where to look first
Pilot lights only while the button is held
The flame appears, but it drops out the moment you release the control.
Start here: Start with the thermocouple tip position in the flame, the thermocouple connection at the gas control, and a weak pilot flame.
Pilot stays lit briefly, then goes out
It holds for a minute or longer, then shuts off on its own.
Start here: Look hard at venting, backdraft, dirty combustion air openings, and signs of overheating or rollout.
Pilot is small, lazy, or yellow
The flame is not sharp blue and may flutter, split, or barely touch the sensor.
Start here: Check for a dirty pilot assembly, lint or dust in the burner area, and air movement around the heater.
Most likely causes
1. Weak or misdirected pilot flame
A pilot that is too small, yellow, or not wrapping the thermocouple cannot generate a strong enough hold signal.
Quick check: Watch the pilot through the sight opening. You want a steady blue flame that directly heats the thermocouple tip.
2. Loose or failing water heater thermocouple
If the pilot looks decent but drops out as soon as you release the control, the thermocouple circuit is a top suspect.
Quick check: Make sure the water heater thermocouple is seated in the flame and snug where it threads into the gas control.
3. Draft or venting problem
Backdraft, a blocked vent, or strong air movement can pull the flame off the sensor or trip safety behavior after ignition.
Quick check: With the burner off, hold a smoke source near the draft hood area only if you can do it safely; smoke should be pulled into the vent, not spill back into the room.
4. Gas control fault or internal safety issue
If the flame is correct, the vent is drafting properly, and the thermocouple connection is sound, the gas control may not be holding the pilot circuit.
Quick check: This becomes more likely only after the flame, thermocouple placement, and venting checks all look right.
Step-by-step fix
Step 1: Confirm the exact failure pattern before touching anything
A pilot that never lights, one that drops out instantly, and one that dies after a short run do not get diagnosed the same way.
- Turn the gas control to pilot only if you are following the lighting instructions on the heater label.
- Watch through the viewing area and note whether you get no flame, a brief flame, or a flame that holds only while the button is pressed.
- Look for obvious warning signs: soot, scorch marks, melted wiring, water dripping onto the burner area, or a strong gas smell.
- Check whether nearby doors, fans, or open windows are creating noticeable air movement around the heater.
Next move: You now know which path fits your heater instead of guessing at parts. If you cannot safely see the flame behavior or the area shows soot, scorching, or water intrusion, stop and call a pro.
What to conclude: The flame pattern and timing tell you whether to focus first on ignition, flame sensing, or venting.
Stop if:
- You smell gas before or during relighting.
- You see soot, scorch marks, or melted insulation around the burner compartment.
- Water is dripping into the burner area or the floor is wet around the base.
Step 2: Check the pilot flame and clean out simple burner-area debris
A dirty pilot opening or lint around the burner is one of the most common reasons a pilot flame gets too weak to hold.
- Turn the gas control off and let the burner area cool.
- Remove the outer access cover if your heater has one and inspect for lint, dust, rust flakes, or spiderweb debris around the burner compartment opening.
- Use a vacuum with a narrow attachment to remove loose debris from the accessible burner area. Do not force anything into the pilot opening.
- Relight the pilot and watch the flame. A healthy pilot is usually steady blue and strong enough to engulf the upper portion of the thermocouple tip.
Next move: If the pilot flame becomes stronger and now stays lit, the problem was likely restricted combustion air or a dirty pilot area. If the flame is still tiny, yellow, or blowing off the sensor, move to thermocouple position and vent checks.
What to conclude: A weak flame points to a pilot assembly issue, dirty air path, or draft disturbance more than a bad gas control.
Step 3: Inspect the water heater thermocouple position and connection
If the pilot lights but dies when you release the button, the water heater thermocouple is the first component to verify after the flame itself.
- With the heater off and cool, look at where the water heater thermocouple tip sits relative to the pilot flame.
- Make sure the tip is directly in the pilot flame path, not bent away or sitting below it.
- Check the threaded thermocouple connection at the gas control. It should be snug, not cross-threaded or finger-loose. Do not overtighten it.
- Relight the pilot and hold the control as directed on the label long enough for the thermocouple to heat fully, then release it.
Next move: If the pilot now holds, the issue was poor flame contact or a loose thermocouple connection. If the pilot flame is good and the connection is snug but it still drops out right away, the water heater thermocouple is a supported replacement suspect.
Step 4: Rule out venting and draft problems before blaming the control
A water heater can light normally and still lose the pilot if the vent is blocked, backdrafting, or pulling the flame off the sensor.
- Check the area around the heater for strong air movement from exhaust fans, return-air pulls, open exterior doors, or a very tight utility room.
- Inspect the visible vent connector above the heater for loose joints, heavy rust, sagging sections, or obvious blockage at the draft hood area.
- After the heater has been off, perform a simple draft check only from outside the vent path: smoke near the draft hood should be drawn upward, not spill back into the room.
- If the pilot stays lit only with a door open or only when fans are off, treat that as a venting or combustion-air problem, not a parts-shopping problem.
Next move: If correcting room air movement changes the pilot behavior, you have narrowed it to draft or combustion air rather than a failed sensor. If draft looks normal and the pilot flame is still solid but the pilot will not hold, the remaining likely cause is the thermocouple or gas control.
Step 5: Replace the supported part only if your checks clearly point there, or call for gas-service repair
Once the flame, thermocouple position, and venting checks are done, you can make a cleaner decision instead of guessing.
- Replace the water heater thermocouple if the pilot flame is strong and blue, the tip is properly in the flame, the connection is snug, and the pilot still dies when you release the control.
- Do not buy a gas control just because the pilot will not stay lit. On this symptom, gas control replacement is a pro-level call after the earlier checks are ruled out.
- If the pilot drops out after a few minutes, or you found draft spillage, soot, or vent damage, schedule qualified service for combustion and vent diagnosis.
- After any repair, relight the pilot, let it sit, then run hot water and confirm the main burner lights cleanly and the pilot remains stable.
A good result: A successful repair gives you a pilot that stays lit, a clean burner ignition, and normal hot-water recovery.
If not: If a confirmed thermocouple replacement does not fix a good-flame, good-draft heater, stop there and have the gas control and combustion system professionally checked.
What to conclude: At this point you have either solved the common failure or narrowed it to a gas-side control problem that should not be guessed at.
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FAQ
Why does the pilot go out as soon as I release the button?
That usually means the water heater thermocouple is not getting a strong enough signal. The most common reasons are a weak pilot flame, the thermocouple tip sitting out of the flame, a loose thermocouple connection, or a worn thermocouple.
Can a dirty pilot really cause this?
Yes. A partially restricted pilot opening can make a small lazy flame that looks lit but does not heat the thermocouple well enough to hold the pilot circuit open.
Should I replace the gas control first?
No. On this symptom, I would check flame quality, thermocouple position, thermocouple connection, and venting first. Gas controls do fail, but they are not the first part to guess at.
What if the pilot stays lit for a few minutes and then goes out?
That pattern leans more toward draft, venting, combustion-air, or overheating trouble than a simple loose connection. If you see draft spillage, soot, or flame disturbance, stop and get qualified service.
Is it safe to keep trying to relight the pilot?
Not repeatedly. A couple of careful attempts while you observe the flame behavior is one thing. Repeated relights without checking for gas smell, draft problems, or soot can make an unsafe situation worse.
Can I replace a water heater thermocouple myself?
Many homeowners can, if access is straightforward and the repair does not require disturbing sealed gas piping or complex burner assemblies. If the burner assembly is hard to remove, the vent is suspect, or you are unsure about leak checking, call a pro.