Has your boiler's pilot light gone out? What are the main causes? Here we explain, along with solutions and costs.
Boilers have come a long way over the years.
One feature you won’t find on modern models is the pilot light - that small, ever-burning flame that older boilers rely on to ignite the gas.
If your boiler still has a pilot light and it’s gone out, you might be wondering what to do.
So, what exactly is a boiler pilot light, why does it go out, and how can it be relit safely?
Let’s take a closer look.
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What is a Boiler Pilot Light?
As mentioned, boiler pilot lights are found in older boilers, although they can also be found inside older furnaces.
The purpose of a boiler pilot light is to act as the flame needed to light the gas coming from the main burner.
In this setup, a continuous flow of gas is released via the gas pipe.
As a result, the flame can light the gas and create a continuous burn.
But what if the pilot light goes out?
Why Pilot Lights Go Out
⚠️ Important: If you smell gas, leave the property immediately and contact National Gas Emergencies on 0800 111 999.
When a pilot light goes out, gas could continue to flow, which is obviously dangerous. Thankfully, older boilers are built with safety mechanisms to prevent this.
Inside the pilot light tube is a sensor (thermocouple) that detects whether the flame is burning. If it goes out, the sensor automatically cuts the gas supply to prevent any build-up.
Relighting a Boiler Pilot Light
Only a Gas Safe registered engineer can legally and safely relight a pilot light.
Trying to do it yourself isn’t just risky - it’s against the law.
A DIY attempt could lead to gas leaks, fire, or even an explosion. For your safety (and everyone else’s), always hire a qualified heating engineer.
Why Is My Boiler Pilot Light Continually Going Out?
If you find that your boiler pilot light keeps going out, there are several likely explanations.
Whatever the case, you’d need to hire a qualified heating engineer to diagnose the cause with certainty before they would also need to solve it.
The most common reasons for a boiler pilot light regularly going out:
The thermocouple is Broken/Faulty
Also known as the flame sensor, this copper rod is directly hit by the pilot flame.
It acts as a safety mechanism that can turn off the gas if it notices that the pilot light has gone out.
The purpose, therefore, of a thermocouple is to prevent a dangerous accumulation of gas.
Of course, it’s possible that a thermocouple could end up misaligned, malfunctioned, broken, or it may even up dirty. If this happens, it will shut off the gas valve and your pilot light won’t be able to stay lit.
Pilot Light Orifice is Dirty
Another possibility is that dirt has built up in your boiler's pilot orifice.
If this has occurred, it may be stopping the flame enveloping the thermocouple as it should be. As a result, the gas would be shut off.
Gas Regulator Is Not Functioning Right
Boiler pilot lights can also go out as a result of a problem with your gas regulator.
If it is not working correctly, it’s possible that your boiler will not receive a sufficient quantity of gas needed for the boiler pilot light to stay lit.
If other gas appliances are acting up, then the gas regulator may be to blame.
So, if you find that several gas appliances are acting up around the same time, you should get in touch with your utility company regarding your concerns.
Of course, if you have any other reason to suspect the gas regulator isn’t functioning right, you should contact them all the same.
Strong Draught
Lastly, even a heavy draught could be the culprit. If you notice that your boiler’s pilot light tends to go out on days that are especially windy, then a strong draught may be to blame.
Of course, coincidences do happen, but if you notice a trend, there’s a good chance that a draught is a problem.
While draughts themselves can be addressed DIY, you should still hire a qualified heating engineer if your pilot light keeps going out, whatever the reason.
After all, you can’t be sure that a draught is a cause until a professional look at your boiler.
Moreover, the heating engineer will be able to solve this issue in the most optimal way and, if a draught is to blame, help you determine how to best deal with it.
Cost to Relight or Repair a Pilot Light
If your pilot light simply needs relighting, costs are usually modest.
However, if there’s an underlying fault (such as a broken thermocouple), prices will vary depending on the repair.
Here’s a rough guide:
Relighting a Boiler Pilot Light: £30 to £120
Fixing a Thermocouple: £30 to £120
Replacing a Thermocouple: £120 to £180
Cleaning Out a Pilot Light Orifice: £30 to £120
Replacing a Pilot Light Orifice: £40 to £130
If the issue lies with your gas regulator, your utility company will likely handle it - often free of charge.
In the case of draughts, you may just pay a callout fee (£30–£120), and then fix the draught yourself with draught excluders, weather stripping, or double glazing, depending on the source.
Boiler Pilot Light Out Conclusion
If your boiler pilot light keeps going out, it’s not something to ignore - it’s a sign your boiler may be on its last legs.
A modern boiler doesn’t rely on a pilot light at all, uses far less gas, and is significantly more efficient and reliable.
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