Troubleshooting a Pilot Light in Water Heaters

A pilot light is a tiny flame that burns continuously in gas-powered home appliances like stoves and heaters. The pilot light’s primary purpose is to ignite the burners when the heater is turned on. This pilot light is never intentionally turned off unless the occupants are leaving the premises for an extended period.

The pilot light is fed by the same gas that supplies the burners in the system. It is located within the system and is ventilated so there that there is no danger of carbon monoxide leeching into the home. The existence of the pilot light makes it convenient for the appliance to come on when ti needs to without you having to go down to the basement to light the boilers.

Some people are concerned about the dangers of a gas leak if the pilot light blows out. The safety mechanism that is employed in most units takes care of the gas in the event the light goes out. There is a thermocouple that prevents gas from leaking out when the pilot light is off.

The thermocouple is a little device that senses heat and generates a tiny amount of electricity. This small amount of electricity is used to power a small electromagnet. When in the powered state the electromagnet keeps the gas valve open, allowing the pilot light to be supplied with gas.

The moment the light goes out, the thermocouple is no longer heated. When it cools down, which is fairly instant, it stops generating electricity. When there is no electricity the electromagnet fails and shuts the vale. The supply of gas is stopped.

This system has been in use for decades and has proven itself without a doubt. That is the reason it is used in most heaters and stoves. As reliable as it is, it is possible to encounter failure from time to time. In most cases, you can troubleshoot the problem and get it rectified. If you can’t then you need to get a professional to attend to it.

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Potential Problems

Several problems that could arise that extinguishes this pilot light include the following six which you could most likely rectify once you confirm its cause. They include the existence of condensation, the lack of proper ventilation, the pilot light won’t reignite, or the pilot light won’t remain ignited, the flame may be too big, or the flame is too small. We will look at each in turn.


If their s too much condensation forming above the pilot lamp’s position and water us dripping onto the pilot lamp, it could blow the fire out. If your flame has indeed gone out, this is the first thing to diagnose as it is the easiest to fix and the most common problem to have. Wipe the condensation and then go through your relight procedure according to the manufacturer’s instruction.


The lack of proper ventilation in the chamber will cause carbon dioxide to build-up in the chamber. The pilot lamp, even though being fed by gas, still needs oxygen to burn. If it’s not getting oxygen, it is because the carbon dioxide that is the byproduct of the flame has no place to go and it is choking out the flame. To fix this, find the ventilation points and make sure nothing is blocking it and that it is able to exhaust the gasses and take in fresh air. Then proceed to relight the lamp.

Unable to Reignite

The chances are that the lamp is not getting a stable supply of gas. This is usually because the tube is blocked with soot from dirty burning. Dirty flames produce carbon deposits that tend to clog the tubes and eventually snuff out the gas supply. You either have to remove it and clean it according to the manufacturer’s instructions, or you will have to get it replaced. Check your manual for replacement procedures.

Unable to Stay Ignited

If you are able to light the lamp but it does not stay lit for long, then you have a different kind of a problem. It is most likely that the thermocouple or the electromagnet that is holding the valve open is not keeping it in the open position. You would probably need to replace the entire assembly.

Large Flame

You do not want too large a flame for a couple of reasons. First, its a waste of gas. Second, a larger flame than normal indicates that there is a leak in the system – most likely in the valve assembly, and the tube is getting more gas than it needs. It is also possible that there is increased pressure in the system. In either case, you should have a certified technician take a look at it.

Small Flame

A small flame is also a problem. It would then lead to other problems like the inability to stay ignited. The most probable problem with this is that there is a build-up in the orifice of the pipe. If you have the instructions to disassemble it, take it out and have it cleaned and replaced. If it’s still not doing the trick, there may be a problem with the gas pressure. You will need to call the technician or the gas company.

Other Problems

There is another problem that is sometimes stumbled upon. That is when the flame is not the bright blue that is supposed to be. The gas that is coming in is clean and always burns blue. If it is burning yellow, it indicates that there is dirt in the system or at the orifice. It needs to be cleaned or serviced. If there is nothing here that seems to work and the lamp does not common after you have tried lighting the thermocouple and it is still not allowing gas to pass into the tube, then there is a good chance that the thermocouple itself is inoperative. You will have to call your technician.

As a precaution, it is always best that you turn off the main gas valve. There isn’t a risk of fire as much as there is a risk of asphyxiation if there is a leak that is slow and not immediately detectable. Keep the area well ventilated and only conduct cleaning and repairs with the proper tools and instruction manuals.

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