Pilot will light only while you hold the button
You can get a small flame at the pilot, but it dies as soon as you release the control.
Start here: Start with the pilot flame shape, burner compartment dirt, and the thermocouple connection area.
Gas water heater troubleshooting
Water Heater Flame Goes Out After Starting
Direct answer: When a water heater flame starts and then goes out, the usual causes are a venting or draft problem, a dirty pilot or burner area, or a weak thermocouple-style flame-sensing setup. Start with airflow and visible flame checks before blaming the gas control.
Most likely: On a standard tank gas water heater, the most common real-world pattern is a weak pilot flame or dirty burner compartment that will light briefly but will not stay proven.
First separate the pattern: pilot goes out, main burner goes out, or the whole unit shuts down after a few seconds. That tells you whether you are dealing with flame sensing, draft, or a larger combustion problem. Reality check: a water heater that worked for years can quit from plain dust, lint, or a new draft condition. Common wrong move: holding the pilot button longer and longer without checking why the flame is weak in the first place.
Don’t start with: Do not start by replacing the gas control valve or taking apart sealed combustion parts you are not sure how to reassemble.
If you smell gas or see scorch marks,stop and call the gas utility or a qualified service tech.
If the flame is lazy, yellow, or blowing around,check venting and burner air before buying parts.
Last reviewed: 2026-04-05
What kind of flame shutdown are you seeing?
Pilot stays lit but main burner goes out soon after ignition
The burner lights normally, runs briefly, then shuts down before the tank is heated.
Start here: Start with vent draft behavior, flame appearance, and signs of overheating or rollout near the burner opening.
Flame is unstable, yellow, or wavering
Instead of a steady blue flame, it flickers, lifts, or looks soft and lazy.
Start here: Start with air intake blockage, lint, dust, and venting problems.
Unit worked before but now drops out repeatedly
It may relight, run for a short time, then quit again later the same day.
Start here: Start with recent changes around the heater like storage piled nearby, a new exhaust fan, or a loose vent section.
Most likely causes
1. Dirty pilot opening or burner compartment
Dust, lint, and rust flakes can weaken the pilot flame so it no longer wraps the flame sensor properly.
Quick check: Watch the pilot through the view port. A healthy pilot is steady and mostly blue, not tiny, split, or barely touching the sensor tip.
2. Draft or venting problem
A blocked, loose, or backdrafting vent can disturb the flame or trip safety shutdown behavior shortly after ignition.
Quick check: Look for melted plastic nearby, soot, hot smells at the draft hood, or vent sections that are loose, rusted, or disconnected.
3. Weak thermocouple or flame-sensing circuit
If the pilot looks decent but drops out when you release the control, the flame sensor path may be failing.
Quick check: Confirm the pilot flame fully envelopes the thermocouple tip. If it does and the pilot still will not hold, the sensor branch becomes more likely.
4. Restricted combustion air or overheated burner area
Closets packed with storage, clogged intake screens, or heavy lint can starve the burner and cause unstable combustion.
Quick check: Clear the area around the heater and inspect lower intake openings or screens for dust mats, pet hair, or debris.
Step-by-step fix
Step 1: Pin down which flame is actually going out
Pilot dropout, main burner dropout, and full shutdown look similar from across the room, but they point to different fixes.
- Stand where you can safely watch the burner view area without removing sealed covers.
- Light the unit only if you are following the normal lighting instructions already printed on the heater.
- Note whether the pilot dies when you release the control, or whether the pilot stays lit and only the main burner drops out later.
- Look at flame color and behavior: steady blue is normal, while yellow tips, fluttering, lifting, or a flame that seems to blow sideways points to air or vent trouble.
Next move: You now know whether to focus on pilot holding, burner stability, or venting behavior. If you cannot clearly see the flame, hear a whoosh, or the unit behaves erratically, treat it as a combustion safety issue and stop.
What to conclude: A pilot that dies immediately usually points to flame sensing or a weak pilot. A burner that starts then drops out leans more toward draft, air, or overheating problems.
Stop if:
- You smell gas at any point.
- You see soot, scorch marks, or melted wiring or plastic.
- The burner flames roll out of the chamber instead of staying contained.
Step 2: Check for obvious draft and vent problems first
A bad draft can snuff or destabilize the flame, and it is one of the more important safety checks before you touch anything else.
- With the heater off and cooled down, inspect the vent connector from the draft hood to the chimney or vent run.
- Look for disconnected joints, sagging sections, rust holes, bird or debris signs, and anything stored against the draft hood area.
- Check whether a strong bath fan, kitchen hood, or nearby exhaust fan is running when the heater drops out.
- After a brief firing cycle, carefully feel for unusual heat spilling from the draft hood area rather than moving up the vent. Do not touch hot metal directly.
Next move: If you find a loose or obviously blocked vent condition, correct only simple visible issues like moving stored items away and then retest. If the vent looks intact but you still suspect backdrafting or blockage, stop DIY and have the venting checked professionally.
What to conclude: Flame problems tied to venting are not good parts-shopping problems. They are safety and combustion problems first.
Step 3: Clean the burner area and air intake openings
This is the most common low-cost fix when the flame is weak, lazy, or unstable, especially in garages, laundry areas, and utility closets.
- Turn the gas control to off and let the burner area cool fully.
- Vacuum loose dust and lint from around the base of the water heater, the lower air intake area, and the outer burner compartment opening if accessible without disassembly.
- If the heater has an intake screen, clean it gently with a soft brush and vacuum rather than poking debris inward.
- Wipe exterior dust from the area with a dry or lightly damp cloth only. Keep water and cleaners out of the burner compartment.
- Relight the heater normally and watch whether the pilot and burner flames are now steadier and bluer.
Next move: If the flame now stays lit and looks stable, the problem was likely restricted combustion air or debris around the burner area. If the pilot is still weak or the burner still drops out, move to the pilot flame check.
Step 4: Judge the pilot flame before you replace anything
A weak pilot is the classic reason the flame goes out after starting, and you can often confirm that by sight.
- Relight the pilot and watch the flame through the view opening.
- Look for a pilot flame that is strong enough to wrap the thermocouple tip or flame sensor area, not just barely touch it.
- If the flame is tiny, split, yellow, or easily disturbed, the pilot opening may be dirty or the burner assembly may need service.
- If the flame looks strong and properly aimed but still drops out when you release the control, the thermocouple branch becomes more likely.
- Check that any visible thermocouple connection at the gas control is snug, not cross-threaded or obviously loose. Do not overtighten.
Next move: If tightening a visibly loose thermocouple connection restores normal pilot holding, monitor a few full heating cycles before calling it fixed. If the pilot remains weak or will not hold despite a good-looking flame, stop short of deeper gas-valve work unless you are experienced with this heater design.
Step 5: Decide between a supported repair and a pro call
By this point you should know whether you have a simple pilot-sensing problem or a larger combustion issue that should not be guessed at.
- If the heater is a standing-pilot model, the pilot flame is properly shaped, and the pilot still drops out when you release the control, replace the water heater thermocouple with the correct style and length for your unit.
- If cleaning the intake and burner area restored stable flame, keep the area clear and verify several complete heating cycles over the next day.
- If the main burner still lights and then shuts down, or you have any sign of vent spillage, rollout, soot, or repeated overheating, stop and schedule service for combustion and vent diagnosis.
- If you actually have an electric water heater with no flame at all, use the electric no-hot-water path instead. If you have a tankless unit that starts hot then goes cold, use the tankless temperature-drop path instead.
A good result: A successful thermocouple replacement or cleaning result should give you a steady pilot and a burner that completes a normal heating cycle without dropping out.
If not: If the new thermocouple does not solve a standing-pilot dropout, or your heater uses electronic ignition, the remaining causes are usually in the gas control, burner assembly, or venting and are better handled by a pro.
What to conclude: This is where you stop guessing. Replace the thermocouple only when the pilot pattern supports it. For venting, rollout, or electronic ignition issues, the safe next move is service.
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FAQ
Why does my water heater light and then go out a few seconds later?
Most often the flame is not being sensed reliably, or the burner is losing stable combustion. On standing-pilot models that usually means a weak pilot flame, dirty burner area, or failing thermocouple. If the main burner starts and then drops out, venting and draft problems move higher on the list.
Can a dirty water heater really make the flame go out?
Yes. Lint, dust, and debris around the intake or burner area can starve the flame for air or weaken the pilot enough that it will not stay proven. This is especially common in garages, utility closets, and laundry areas.
Should I replace the gas control valve first?
No. That is an expensive guess and not the usual first fix. Check flame shape, intake blockage, and venting first. On a standing-pilot heater, a supported thermocouple diagnosis is much more common than a confirmed gas control failure.
How do I know if it is a vent problem instead of a thermocouple problem?
A thermocouple problem usually shows up as a pilot that will not stay lit even when the pilot flame looks properly aimed. A vent problem more often shows unstable burner flame, shutdown after the burner has been running, soot, hot smells, or exhaust spilling near the draft hood.
What if I have no flame because my water heater is electric?
Then this is the wrong symptom path. Electric water heaters do not use a burner flame, so move to an electric water heater no-hot-water diagnosis instead. If you have a tankless gas unit that starts hot and then goes cold, use the tankless temperature-drop path.