Fixed: Why Does Pilot Light Keeps Going Out On Water Heater

Tired of unexpected cold showers and wondering why does the pilot light of your water heater keeps going out? Let’s find out why and how to fix it. 

The most common reasons in my experience, for the water heater pilot light to frequently go out, are blocked air filter, dirty or malfunctioning thermocouple, and lack of combustion air. 

It usually occurs with an old water heater but problems can happen with new units as well. 

It’s normal and fine for the pilot light to go out once in a while which can happen due to a sudden air draft. But if it keeps going out and out then there’s something wrong going on with your gas water heater. We will talk in brief about that and tell you what exactly you should be doing in this scenario so as to fix the issue yourself without having to call the technician but first,

What is the pilot light in the water heater?

Simply put, the pilot light is a small tiny burner that is alight all the time so that when the main burner is to be lit, the ignition is started with the help of this pilot light. It’s there so that you won’t have to use a match or lighter and manually light the water heater every time water is needed to be heated. Also read: Water heater leaking? Here’s what to do.

So with that said, let’s jump straight into the main part. 

5 Reasons pilot light keeps going out on water heater

Safety advice

Before we move on to the diagnostic and fixing process, it’s best if you close the gas supply to the water heater and wait for a few minutes for any gas to dissipate. 

1. Dirty or clogged air filter grate

The air filter grate in your water heater is an important part that supplies oxygen for the combustion of gas. It’s from where your pilot light breaths. It’s the most common culprit.

The air filter grate can be located under the tank or on some models on the bottom side. 

What you have to do is clean and unclog it. Take a long dusting brush and try to clean the underneath of the tank. You will want to scrape the base of the tank. 

Once done, now try to reignite the pilot light and see if it stays. If it goes out again then move on to the next step. 

2. Suffocated water heater surrounding

As we discussed in the section above, the gas water heater requires air to breathe I. E. For combustion. 

Look around and see if the surrounding of the tank is highly populated with stuff or it’s open enough for airflow. 

If it’s the first case then that’s what might have been the culprit. Free up some space around it so air can easily vent in. Try lighting it again. Move to the step if goes out again. 

3. Dirty or dislocated thermocouple


Another common issue that I have seen with the inconsistently lit pilot light is the problem with thermocouples

A thermocouple is the CPU and safety mechanisms of your gas water heater. It sits on the top of the pilot light. When the pilot light is on, the thermocouple generates a small voltage that tells the system to keep the gas flow free. If for some reason the voltage is not generated, the system assumes that the pilot light is off (even when it’s not) and switches off the gas supply and then the flame goes out. 

Over time, this thermocouple can catch dirt and grime which in result can prevent it from generating that voltage, and thus flame goes out. Or another situation is that the instrument itself gets bent away due to flame. 

So what you can do here is to try to clean the surface of the thermocouple with the help of fine sandpaper and keep its end as close to the pilot light as possible. Our aim here is to make sure it detects heat. 

If the problem persists then the most likely scenario is that the thermocouple has gone bad. 

4. A bad, faulty thermocouple

It’s not uncommon for this cheap part to go out and become defective. 

If you have tried everything I mentioned above and the pilot light still going out, then the most likely scenario here is of a bad thermocouple. It’s cheap and easy to replace. 

But you will want to test if it’s actually bad before you change it. Check out this video.

The reading on the multimeter should be around 20mV for a functioning thermocouple. 

You can try one last thing just to make sure you have tried everything before actually changing the thermocouple.

5. Dirty pilot tube

A pilot tube is a tiny pipe similar in size to a thermocouple. It feeds the gas to the pilot light to keep it going on. 

It’s just another thing that can catch dirt and clog inside the tube that can reduce the gas flow. 

What you can do here is simple. Take a slender needle and try to clean and unblock the pilot tube. It can take a while to clean. You can also try to blow air from one side if you have dissembled it from the main system. 

Popular questions

If the pilot light goes out on the water heater does the gas leak? 

No, gas won’t leak. The reason your pilot light is going out in the first place is that the gas supply has been stopped due to various reasons mentioned above like bad thermocouple, clogged air filter, pilot tube, etc. Still, if you smell rotten eggs smell then shut off the main gas supply and immediately call your plumber. 

How do you know if you have a bad thermocouple?

Usually, if you have a bad thermocouple, the most common sign you see is if your pilot light keeps going out. And if you do test it on a multimeter and the reading is not in the range of 20mV and then the thermocouple is bad. 

What do you do if your water heater pilot light won’t stay lit?

As I have mentioned in the five-step diagnostic procedure above, check for air filter blockage, bad thermocouples, and ventilation. Any of that could be the reason that keeps your water heater pilot light from staying lit. 

Your call

So that’s it for now. I hope this mini yet, a complete guide to why pilot light goes out on water heater was helpful and fixed your problem. If the problem doesn’t resolve even after doing the suggested above then I advise you to call the technician. Also read: It’s time to upgrade. Switch to the new and efficient top outdoor tankless water heaters.

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