Before anything else
If you smell gas, do not try to relight it. Leave the house, and call the gas utility from outside. A pilot that will not stay lit is usually a faulty part, but a gas smell is a different situation entirely.
Relighting the pilot is easy. A pilot that will not stay lit is telling you a specific part has failed, and which part depends almost entirely on one thing: how long it burns before it goes out.
That timing is the whole diagnosis. Start there.
How Long Does It Stay Lit?
| What happens | Cause | Fix |
|---|---|---|
| Goes out the moment you release the button | Thermocouple, almost always | Replace the thermocouple |
| Stays lit 30 seconds, then dies | Weak thermocouple or a weak pilot flame | Clean the orifice, then replace |
| Burns fine for hours or days, then out | Draft, combustion air, or a clogged flame arrestor | Check airflow and the screen at the base |
| Will not light at all, no gas smell | Gas supply, or the gas control valve | Check other gas appliances first |
| Yellow or lazy flame instead of blue | Dirty orifice or starved of air | Clean the orifice and the arrestor screen |
| Out repeatedly, house has pets or a laundry room nearby | Lint on the flame arrestor | Vacuum the screen |
Rows one and two are a part failure at the pilot assembly. Rows three and six are an air supply problem. Row four is upstream of the heater entirely. Match yours and skip the rest.
1. The Thermocouple
The thermocouple is a thin metal rod sitting in the pilot flame. Heat generates a small electrical current, and that current is the only thing telling the gas valve it is safe to stay open. No current, no gas. It is a safety device working exactly as designed.
When it degrades, it produces less current than the valve needs, so gas shuts off the moment you stop holding the override button.
The tell
Hold the pilot button down for a full 60 seconds rather than 20 or 30. If the flame holds while you hold the button and dies the instant you release, the thermocouple is not generating enough current.
Before replacing it, look at where the tip sits. It should be engulfed in the flame, not beside it. A thermocouple that has drifted out of position produces the same symptom as a failed one and costs nothing to correct.
Newer units with electronic gas controls use a thermopile rather than a thermocouple. Same principle, more voltage, different part, and it is not interchangeable.
2. The Flame Arrestor Screen, the One Nobody Checks
Every residential gas water heater sold since 2003 is built to the FVIR standard, short for Flammable Vapor Ignition Resistant. Part of that design is a flame arrestor screen at the base of the unit, which draws in all the combustion air.
That screen catches everything in the air around it. The industry term for what clogs it is LDO: lint, dust and oil.
Once it is blocked, the burner is starved of air. The flame goes lazy, the pilot cannot hold, and on many units a one-shot thermal switch built into the thermocouple trips and shuts the heater down.
Why this one matters more than it should
That thermal switch is one-shot. It does not reset. Once it trips, the part has to be replaced, so a clogged screen turns a vacuuming job into a parts call.
It is also the reason a pilot goes out repeatedly after being relit correctly. Manufacturer guidance is to brush or vacuum the screen a couple of times a year.
Who gets this most
- Water heaters in the laundry room. Dryer lint is the worst offender on this list.
- Houses with pets. Hair mats the screen faster than dust alone.
- Garage installs, which are common across Houston and are dustier and draftier than an interior closet.
- Any unit that has never been serviced, because nobody thinks to look at the bottom of the tank.
3. A Clogged Pilot Orifice
The pilot gas exits through a very small opening. Dust and scale narrow it, and a narrowed orifice produces a weak flame that cannot heat the thermocouple properly and is easily blown out.
A healthy pilot flame is steady, blue, and wraps around the thermocouple tip. Yellow, flickering, lifting away from the tip or noticeably small all point at the orifice.
Cleaning it means shutting off the gas, removing the burner assembly and clearing the opening without enlarging it, which is why it is worth having done rather than improvised with a paperclip.
4. Drafts and Combustion Air
If the pilot burns for hours or days and then goes out, it is being extinguished rather than failing. Look for what changed.
- The closet door, now kept closed when it used to be open. That alone can starve a heater of air.
- A new exhaust fan, range hood or dryer, pulling enough air to reverse draft at the flue.
- Gaps around the flue or a disconnected vent section, letting outside wind down onto the burner.
- Storage stacked against the unit, blocking the air the arrestor screen needs.
A simple test: does it go out on windy days, or when the dryer runs? Either answer points at air rather than parts.
5. The Gas Valve or Gas Supply
Before assuming the water heater, check whether other gas appliances are working. If the stove and the furnace are also out, the problem is supply, not the heater.
If everything else runs normally and the pilot still will not light, the gas control valve itself may be failing. That is the most expensive item on this page and often the point where replacing the unit makes more sense than repairing it, particularly past ten years.
If the heater is old enough that the valve is in question, it is worth checking the anode and the tank condition at the same time rather than spending on one part. That decision is set out in anode rod water heater Houston.
How to Relight It Properly
- Turn the gas control knob to OFF and wait five full minutes. This lets any unburned gas clear. Do not skip it.
- Turn the knob to PILOT.
- Press and hold the reset button while lighting the pilot, using the igniter if the unit has one or a long lighter through the viewport.
- Keep holding for a full 60 seconds after it lights. Most people release at 20 and blame the thermocouple.
- Release slowly. If it holds, turn the knob to ON and set your temperature.
- If it dies on release, try once more holding for 90 seconds. Twice is enough. A third attempt will not change the answer.
Once it is running again, confirm the tank is actually heating rather than just lit. If you have flame but still short hot water, that is a separate problem covered in not enough hot water.
Why Houston Units Do This More
Two local factors stack up.
Garage installs. A large share of Houston water heaters sit in the garage, which is dustier, more humid and far draftier than an interior closet. That is the worst environment for a flame arrestor screen.
Hard water and sediment. Scale on the tank floor makes the burner run longer for the same result, which means more air drawn through the screen and more hours of combustion per day. The same buildup causes the popping described in water heater making noise, so a noisy heater and a failing pilot are frequently the same underlying problem.
Neither is a reason to run the tank hotter. Higher temperatures accelerate scale rather than helping, and the right setting is covered in what temperature to set your water heater to.
Repair or Replace?
| Age and situation | Sensible move |
|---|---|
| Under 8 years, thermocouple failure | Replace the part, inexpensive fix |
| Any age, clogged arrestor screen | Clean it, then service annually |
| Under 10 years, gas valve failure | Price the valve against a new unit first |
| Over 12 years, any major part | Replace the unit, you are past design life |
| Rusty hot water or moisture at the base | Stop repairing, the tank is failing |
Most Houston tanks give out between years eight and twelve. Options and pricing are under water heater repair.
Frequently Asked Questions
Why does my pilot light keep going out?
The timing tells you which part failed. If it dies the moment you release the reset button, the thermocouple is not generating enough current to hold the gas valve open. If it burns for hours or days and then goes out, it is being extinguished by a draft or starved of combustion air, often by a clogged flame arrestor screen at the base of the unit. If it will not light at all, check whether other gas appliances are working before blaming the heater.
How do I know if my thermocouple is bad?
Hold the pilot reset button down for a full 60 seconds rather than the 20 or 30 most people manage. If the flame holds while you hold the button and dies instantly on release, the thermocouple is the likely cause. Before replacing it, check that the tip actually sits inside the flame rather than beside it, because a thermocouple that has drifted out of position produces the same symptom and costs nothing to correct.
What is a flame arrestor screen and why does it make my pilot go out?
Every residential gas water heater sold since 2003 is built to the FVIR standard and has a flame arrestor screen at the base that draws in all the combustion air. Lint, dust and pet hair clog it, the burner is starved of air, the flame goes lazy and the pilot cannot hold. On many units a one-shot thermal switch then trips and shuts the heater down. That switch does not reset, so a clogged screen turns a vacuuming job into a parts replacement.
How long should I hold the pilot button down?
A full 60 seconds after the pilot lights, and 90 on a second attempt. Most people release at around 20 seconds, which is not long enough for the thermocouple to reach operating temperature and generate the current the gas valve needs. Releasing too early produces exactly the same symptom as a failed thermocouple, which is why plenty of working parts get replaced unnecessarily.
Why does my water heater pilot go out when it is windy or when the dryer runs?
Because it is an air problem, not a parts problem. A dryer, range hood or bathroom fan can pull enough air out of a closed space to reverse the draft at the flue and push exhaust back down onto the burner. Wind does the same through gaps around the vent. If the pilot only fails under those conditions, the fix is combustion air and venting rather than a new thermocouple.
Can I clean the pilot orifice myself?
It is not recommended. Clearing it properly means shutting off the gas, removing the burner assembly and cleaning the opening without enlarging it. Poking a paperclip or wire into the orifice widens it, which changes the gas flow and produces a flame that is worse rather than better. The screen at the base of the unit is different and can safely be vacuumed or brushed.
Is a pilot light that keeps going out dangerous?
The pilot failing is a safety system working correctly, because the gas valve is shutting off when it cannot confirm a flame. What is not safe is repeated relighting without finding the cause, or any gas smell. If you smell gas, leave the house and call the gas utility from outside rather than trying to relight anything.
Should I repair the pilot assembly or replace the water heater?
Under about eight years, a thermocouple is an inexpensive part and worth fixing. A clogged arrestor screen is worth cleaning at any age. A failing gas control valve is the expensive item, and past ten years it is usually worth pricing the valve against a whole new unit before committing. Past twelve years, or with rusty hot water or moisture at the base, the tank itself is the problem and no pilot repair changes that.
Relit it twice and it still will not hold?
We diagnose the thermocouple, the arrestor screen, the orifice and the gas valve in one visit and tell you honestly whether it is a part or the tank. Free estimates across Houston.
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