If your boiler won’t turn on, it can be a stressful and inconvenient experience, especially when you rely on it for heating and hot water.
There are several reasons why your boiler might not be working, ranging from simple issues like low boiler pressure to more complex problems like low gas pressure or a frozen condensate pipe.
Understanding the potential causes can help you figure out what’s wrong and whether it’s something you can fix yourself or if you need to call a Gas Safe registered engineer to perform boiler repairs. This guide will walk you through the most common boiler problems and offer practical solutions to get your heating system back up and running.
Why is my boiler not turning on? The 10 most common reasons
How to fix a frozen condensate pipe
4. Issue with thermostat/scheduled timer
How to fix issues with your thermostat
How to fix issues with your gas supply
How to fix boiler pressure issues
How to fix a build-up of sludge
How to fix a faulty fan or gas valve
When to call in a JustFix Gas Safe registered engineer
Why is my boiler not turning on? The 10 most common reasons
There are various reasons why your boiler might not be turning on. Some problems can be fixed easily at home, while others might require the expertise of a qualified engineer.
Below, we’ll explore the most common issues and what you can do about them.
1. Leaking boiler
A leaking boiler is one of the most common issues that can prevent your boiler from turning on. Leaks can occur for various reasons, such as corrosion, pressure issues, or faulty components.
Even a small leak can cause significant problems by lowering the boiler’s pressure or damaging internal parts.
How to fix a leaking boiler
Fixing a leaking boiler usually isn’t a DIY job. If you notice any water around your boiler, it’s crucial to turn off the power supply to the boiler and contact a Gas Safe registered engineer.
Attempting to fix a leak yourself can be dangerous and may void your boiler’s warranty. A heating and gas engineer can locate the source of the leak and safely replace any faulty components.
2. Flame/pilot light issues
The pilot light or ignition flame is essential for your boiler to function. If the pilot light goes out or the flame is weak, your boiler won’t turn on.
This issue is often caused by a faulty thermocouple, draughts, or a build-up of debris.
How to fix pilot light issues
First, check if the pilot light is out. If it is, try relighting it according to your boiler’s manual. Ensure there are no draughts in the area that could extinguish the flame.
If the pilot light won’t stay lit or keeps going out, it’s best to call a Gas Safe registered engineer. They can clean or replace the thermocouple and make sure there’s no further damage.
3. Frozen condensate pipe
During winter, a common problem is a frozen condensate pipe. The condensate pipe removes acidic waste water from your boiler to an outside drain.
If it freezes, the boiler will shut down as a safety precaution.
How to fix a frozen condensate pipe
To fix a frozen condensate pipe, pour warm (not boiling) water over it to thaw it out. Once thawed, reset your boiler to see if it starts working again.
If the problem persists, or if you’re uncomfortable dealing with it, contact a Gas Safe registered engineer for assistance.
4. Issue with thermostat/scheduled timer
Sometimes the issue might not be with the boiler itself, but with the thermostat or timer settings. If the thermostat is set too low or the timer is off, your boiler might not turn on.
How to fix issues with your thermostat
First, check the thermostat to ensure it’s set to a temperature higher than the current room temperature. If your thermostat has a timer, make sure it’s set correctly and that the boiler is scheduled to turn on when needed.
If the thermostat is old or faulty, it might be time to replace it. For modern smart thermostats, ensure the Wi-Fi connection is stable.
If adjusting the settings doesn’t help, or if you’re unsure how to do this, it might be best to call in a professional to avoid damaging the system.
5. Gas supply issues
Your boiler requires a steady supply of gas to operate.
If there’s an issue with your gas supply, such as a closed valve or a disruption in service, your boiler won’t turn on.
How to fix issues with your gas supply
First, check if other gas appliances in your home, like a gas hob or gas fire, are working. If they’re not, you might have an insufficient gas supply, and you should contact your gas supplier.
If other appliances are working, check the gas valve to ensure it’s fully open.
Never attempt to repair gas supply issues yourself—always contact a Gas Safe engineer to handle it safely.
6. Boiler pressure
Boilers need to maintain a certain pressure level to function properly.
If the boiler pressure is too low, your boiler might not turn on. If the boiler pressure is too high, it could trip safety mechanisms and shut off.
How to fix boiler pressure issues
To check your boiler’s pressure, look at the pressure gauge on the front of the boiler. When the boiler is off, it should typically be between 1 and 1.5 bars.
If the pressure is too low, you can repressurise the system by following the instructions in your boiler’s manual. If the pressure is too high, you can release some pressure by bleeding your radiators.
If you’re unsure how to do this or the pressure continues to fluctuate, it’s advisable to contact a professional heating and gas engineer.
7. Corrosion
Corrosion within your boiler can lead to serious problems, including leaks and pressure drops, which can prevent your boiler from turning on.
This is more common in older boilers or those that haven’t been regularly serviced.
How to fix corrosion
Corrosion often requires professional intervention. If you suspect your boiler has internal corrosion, contact a Gas Safe registered engineer.
They can assess the extent of the damage and recommend whether a repair or replacement is necessary.
8. Build-up of sludge
Over time, your central heating system can build up sludge (a mixture of dirt, rust, and debris).
This sludge can block pipes, the pump, or the heat exchanger, leading to inefficiencies or even a complete boiler shut-down.
How to fix a build-up of sludge
If sludge is suspected, a professional power flush of the system may be necessary.
This process uses chemicals and a pump to remove sludge from the system, improving efficiency and preventing future blockages. A qualified engineer should always perform this.
9. Faulty fan or gas valve
The fan and gas valve are crucial components that help your boiler operate safely. The fan pulls in air to mix with the gas for combustion while the gas valve controls the gas flow to the burner.
If either of these components fails, your boiler won’t turn on.
How to fix a faulty fan or gas valve
You should not attempt to fix these parts yourself.
If you suspect the fan or gas valve is faulty, turn off the boiler and contact a Gas Safe registered engineer. They can diagnose the problem and replace the faulty components.
10. Boiler needs replacing
If your boiler is old and has had multiple issues, it might be time for a replacement. Modern boilers are more efficient and safer and come with warranties that provide peace of mind.
For more information on the costs of replacing your boiler , including the types of boilers available and installation costs, check out our comprehensive guide.
When to call in a JustFix Gas Safe registered engineer
While some boiler issues can be resolved with simple fixes, others require the expertise of a professional. If your boiler won’t turn on and you’re unable to identify or fix the problem yourself, it’s time to call a Gas Safe registered engineer to carry out the boiler repairs. They have the training and experience to safely diagnose and repair a wide range of boiler issues.
At JustFix, our trusted team of heating and gas engineers is available to help with all your boiler needs. We offer transparent pricing with no hidden costs, so you can be sure you’re getting the best service at a fair price. Whether it’s a quick repair, a full system inspection, or a boiler replacement, our engineers are here to help.
Don’t let a faulty boiler leave you in the cold. Book an appointment with a qualified engineer from JustFix today and get your heating system back up and running quickly and safely.
