The basic reset: relight the pilot light
A reset on a gas hot water heater usually means relighting the pilot light after it has gone out. The pilot is a small flame that ignites the main burner when your tank needs heat. If your water is cold and the pilot is dark, you need to turn the control knob to the "Pilot" position, hold down the ignition button, and use a long lighter or match to ignite the flame at the pilot opening — a small tube near the bottom of the tank.
Once the pilot stays lit on its own (usually after 30 seconds of holding the button), turn the knob to "On" or the desired temperature setting. The main burner should ignite within a minute. If the pilot lights but goes out when you release the button, the thermocouple — a safety sensor — may be dirty or failing, and you will need to clean or replace it.
Key Takeaways
- A reset means relighting the pilot light, which sits at the bottom of the tank near the control knob.
- Turn the knob to "Pilot," press the ignition button, and use a long lighter to ignite the small flame opening.
- Hold the button for 30 seconds after the pilot lights to let the thermocouple warm up and sense the flame.
- If the pilot lights but will not stay lit, the thermocouple is likely dirty or worn and needs cleaning or replacement.
- If you smell gas but cannot get the pilot to light, turn off the gas valve, wait five minutes, and call a technician.
When to turn the knob to "Pilot" versus "On"
The control knob has three positions: "Off," "Pilot," and "On" (or a temperature number). When you first relight after the pilot has gone out, you must start at "Pilot" — this position lets gas flow only to the pilot burner, not the main burner. If you turn directly to "On," gas will flood the tank and you risk a dangerous buildup.
Once the pilot flame is steady and you have held the ignition button for 30 seconds, the thermocouple has warmed enough to signal that the pilot is burning. At that point, turn the knob to "On" or your desired temperature. The main burner will light from the pilot flame. If the main burner does not ignite within a minute, turn back to "Off," wait a few minutes, and try again.
How to clean the thermocouple if the pilot won't stay lit
The thermocouple is a thin metal rod that sits in the pilot flame. When it senses heat, it tells the gas valve to stay open. If the pilot lights but goes out as soon as you release the ignition button, the thermocouple is usually clogged with dust or corrosion and cannot sense the flame.
To clean it, turn the gas valve to "Off" and wait five minutes. Locate the thermocouple — it is the thin rod running into the pilot flame area. Use fine-grit sandpaper or a small wire brush to gently scrub the tip until it is shiny. Wipe away any dust with a dry cloth. Then return to the "Pilot" position and try relighting. If it still will not hold, the thermocouple has likely failed and needs replacement.
What to do if you smell gas but the pilot won't light
Gas smell with no flame is a sign that gas is flowing into the tank but not igniting. Do not keep trying to light it. Turn the control knob to "Off" when ready and turn the main gas valve (the lever on the gas line entering the tank) to the off position as well.
Open windows and doors to ventilate the space, then wait at least five minutes before attempting anything else. If you still smell gas after ventilation, or if the pilot will not light after you have tried twice, do not attempt further resets. Call a licensed technician or your gas company's emergency line. A gas leak or a failed ignition system requires professional diagnosis.
Difference between a reset and replacing the igniter
A reset is relighting a pilot that has straightforward gone out — the system is working, the flame just needs to be restarted. If your pilot goes out regularly (more than once a month) or will not stay lit even after cleaning the thermocouple, the igniter or thermocouple itself has failed and needs replacement, not just a reset.
Replacement of these parts requires turning off the gas, draining the tank partially, and unscrewing the old part to install a new one. This is not a reset and is beyond a basic restart. If your pilot keeps dying, a technician can diagnose whether the thermocouple, the igniter, or the gas valve is the problem.
How long a reset should take
A successful reset takes about two to three minutes from start to finish. Turn the knob to "Pilot," press the ignition button, light the flame with a long lighter, hold for 30 seconds, then turn to "On." The main burner should ignite within another minute. If you have not seen a steady flame after five minutes of trying, stop and wait ten minutes before trying again — repeated attempts can flood the tank with unburned gas.
If the reset works, you should hear the main burner roar to life and feel heat building in the tank within 15 to 20 minutes. If the tank does not warm up after an hour, the main burner may not be igniting properly, and you should turn off the gas and call for service.
When to call a technician instead of resetting
Reset the pilot yourself if it has straightforward gone out and you can relight it easily. Call a technician if any of these are true: the pilot will not light at all after two attempts, the pilot lights but will not stay lit even after cleaning the thermocouple, you smell gas but see no flame, the main burner will not ignite after the pilot is lit, or the tank is not heating water even though the burner is running.
A technician can test the thermocouple, igniter, gas valve, and burner assembly to find the real problem. Trying to force a reset when a part has failed can waste time and create a safety risk. Most water heater repairs cost less than the cost of a new tank, so calling early is usually the right choice.
Frequently Asked Questions
How long should I hold the ignition button down?
Hold it for 30 seconds after you see the pilot flame light. This gives the thermocouple time to warm up and sense the heat. If you release too early, the thermocouple will not signal the gas valve to stay open, and the flame will go out.
Can I use a regular lighter instead of a long lighter?
A long lighter or long-reach match is safer because it keeps your hand farther from the flame and the hot tank. A regular lighter can work, but you risk burning your fingers on the tank or the ignition area. A long lighter costs a few dollars and is worth the safety margin.
What if the pilot light keeps going out after I reset it?
A pilot that goes out repeatedly usually means the thermocouple is dirty or failing. Try cleaning it with fine sandpaper first. If it still goes out, the thermocouple or the gas valve needs replacement — this requires a technician.
Is it safe to reset the pilot myself?
Yes, relighting the pilot is a safe task if you follow the steps: use "Pilot" mode, hold the ignition button, and light the flame. The "Pilot" position limits gas flow so there is no dangerous buildup. If you smell gas or cannot get the flame to light, stop and call a technician.
How do I know if the reset worked?
The pilot flame should burn steadily and stay lit when you turn the knob to "On." The main burner should ignite within a minute, and you should hear a roaring sound. The tank should begin warming up — you will feel heat near the bottom within 15 to 20 minutes.