Eco Happy (Solar Expert)

Published February 28, 2024

When your boiler isn’t working as it should, it can have a big impact on your daily life, and it’s tricky to identify the issue and even harder to resolve it.

No heating in the house during a cold snap? Or have you turned on the shower and been blasted by freezing water? We’ve all been there!

That’s why we, at Eco Happy, have created this list of the 9 most common boiler problems and the best ways to fix them. We’ll cover issues like unusual boiler noises, leaks, and much more to get you up to speed!

1. Failure To Provide Heat And Hot Water

If your hot water and central heating system aren’t working, then your boiler isn’t doing any of the things it should be. The tricky thing about this issue is that many different things can cause malfunctions, such as:

  • Low water pressure: When the boiler’s water pressure is low it can prevent hot water from flowing around your home.
  • Faulty thermostat: If your thermostat is malfunctioning, the heating element on your boiler might not be kicking in.
  • Broken diverter valve: The diverter valve directs water to your home’s taps or the central heating system. If it’s broken, water won’t flow to either.
  • Airlocks: Your heating system may be blocked by airlocks.
  • Frozen pipes: If a condensate pipe or multiple pipes are frozen, it can cause blockages.
  • Defective pump: Hot water is unable to circulate properly if the boiler pump isn’t working.
  • Thermostat settings: It could just be the case that your thermostat settings are incorrectly configured.

How to fix it

As you can see, there are plenty of possible causes for this issue and how you fix it will depend on the cause. Generally, if neither your hot water nor heating is working it’s best to call out a Gas Safe registered engineer.

However, we’re going to cover several of the above issues later on and show you how to fix them. So, you may be able to address the cause without an engineer’s help.

2. Unusual Boiler Noise

It’s pretty unsettling when boilers or any other gas appliances start making strange noises. Often, they pass quickly and are nothing to worry about but sometimes they’re a telltale sign of a problem.

The most common unusual boiler noises and their causes are:

  • Whining or buzzing: These sounds are usually caused by a defective burner, worn pump bearings, or another internal issue.
  • Gurgling: This can be caused by trapped air moving through the system or by water quickly passing through the boiler or heating system. If it’s caused by air, then it’s less serious. If it’s caused by a sudden rise in pressure, it will need to be dealt with quickly.
  • Rattling: This can be caused by limescale buildup, a faulty thermostat, or a faulty pump.

How to fix it

Usually, noises like this are a sign that there’s a fairly serious issue with your boiler which can lead to a breakdown and could even cause safety issues if left unaddressed.

So, if you hear any of these noises, you should arrange for a Gas Safe registered engineer to come and take a look.

3. Your Boiler Is Kettling

If your boiler is making popping, bubbling, or whistling noises, this is known as kettling. Mostly, it’s caused by limescale buildup, overheating, or leaks in the system.

A limescale buildup can restrict the flow of water through the system, causing it to make strange noises. If the system is overheating, then the water in the boiler can turn into steam, causing a whistling noise. Finally, leaks in the system can cause the boiler to make unusual noises as it tries to manage the flow of water and pressure.

If you have a combi boiler, it’s less likely to experience kettling but the issue is fairly common in regular and system boilers.

How to fix it

  • Limescale buildup: The best way to fix this issue is to perform a power flush. The process requires the use of specialist equipment and expertise, so you’ll have to enlist an engineer to do it for you.
  • Overheating: If the issue is caused by overheating, you may simply need to lower the temperature on your thermostat or reset it. However, if this doesn’t solve the issue, you’ll need to contact a professional.
  • Leaks: Usually, if there’s a leak in your boiler or heating system, you’ll need to contact an engineer. Still, there are a few steps you can take to try and solve the issue first which we’ll cover in the next section.

4. Leaking Boiler

A leaking boiler is one of the most common boiler problems. Many things can cause it, such as:

  • High boiler pressure: Leaks can occur as excess boiler pressure is released.
  • Corroded components: Normal wear and tear can lead to pipes and other internal components corroding over time. This can cause small holes to appear which lead to leakage.
  • Loose joints and pipe connections: The pipes and joints in a boiler and central heating system contract and expand all the time due to heating and cooling. This can lead to them becoming loose which can cause a leak.
  • Faulty heat exchanger: If the heat exchanger is damaged, it can quickly start leaking.

How to fix it

  • Fixing high boiler pressure: The easiest way to address high boiler pressure is to bleed your radiators which will relieve the pressure on your boiler. To learn how to bleed a radiator, check out our comprehensive guide.
  • Fixing corroded components: If the leak is caused by corroded components, they’ll need to be replaced by an engineer.
  • Fixing loose joints and pipe connections: You could try tightening the joints or pipe connections with an adjustable spanner or pipe wrench. However, these tasks require some skill and knowledge, so it’s usually best to call out an engineer.

If you smell gas at any point while attempting these fixes, turn off the gas supply immediately and call your gas supplier straight away.

5. Pilot Light Keeps Going Out

Another one of the most common boiler problems is a pilot light that keeps going out. This is usually caused by a dirty pilot light orifice, a faulty or dirty thermocouple, a strong draught, or a poorly working gas regulator.

How to fix it

If the thermocouple is damaged, you’ll need to get it replaced by an engineer. If the gas regulator isn’t working properly, you’ll need to turn off the gas supply and contact an engineer immediately.

However, if the issue is caused by a dirty pilot orifice or thermocouple, you should be able to address the issue yourself.

Here’s how to clean a dirty thermocouple:

  1. Make sure the gas supply is turned off.
  2. Find the thermocouple. It’s a small metal rod that sits in the pilot flame. Carefully remove it from the control box and the pilot assembly. To do so, you’ll probably have to unfasten a bracket or clip.
  3. Use an emery cloth or sandpaper to gently clean its tip. Remove any soot, dirt, or oxidation.
  4. Once cleaned, reattach it to the control box and pilot assembly.
  5. Turn the gas on and relight the pilot light.

To clean a dirty pilot light orifice, follow these steps:

  1. Turn the gas off.
  2. Locate the pilot assembly which is usually near the bottom of the boiler and consists of a small gas burner and the orifice.
  3. Carefully remove the assembly. This may involve unclipping or unscrewing it, depending on the model.
  4. Gently clean the orifice using a small brush and ensure you remove all dirt and debris.
  5. Reattach the assembly, turn the gas on, and relight the pilot light.

6. Low Boiler Pressure

Low boiler pressure can be caused by leaks but it may also be the case that the system simply needs to be re-pressurised. You can tell if your boiler has low pressure by checking its pressure gauge. If the reading is lower than 1 bar, this is a sign of low boiler pressure.

How to fix it

If the low pressure is caused by a leak, you can try some of the fixes we suggested earlier or call a Gas Safe registered engineer to assist you.

If you have a modern combi boiler, you may need to re-pressurise the system by allowing more water in. You can do this by using the filling loop on your boiler. The steps to do this can vary between different models, so check the manufacturer’s instructions to ensure you do it correctly.

7. Boiler Switches Off By Itself

There can be several different things that cause a boiler to keep switching off. One of the main causes is low pressure which we’ve already covered.

The other causes include:

  • A faulty water pump
  • An interrupted fuel supply
  • Closed valves

How to fix it

If the issue is caused by an interrupted fuel supply or a faulty water pump, contact an engineer to fix it for you.

Before you do this, you need to check if the issue is caused by closed valves. The main valves you need to check are the isolation valves, located on the flow and return pipes that connect to the boiler.

Follow these steps:

  1. Check the position of each valve’s lever handle. If the handle is perpendicular to the pipe, it’s closed. If it’s in line with the pipe then it’s open.
  2. Depending on the boiler model, there may be stickers indicating when the valves are open or closed.
  3. If the valves are closed, don’t try to open them yourself. Contact an engineer to assist you.

8. Frozen Condensate Pipe

A frozen condensate pipe can cause blockages that disrupt the flow of hot water to your taps and central heating system. Fortunately, it can be one of the easier boiler problems to fix without the help of an engineer.

How to fix it

Slowly pour warm water from a watering can onto the frozen condensate pipe. Or, apply a warm cloth, microwaveable heating pack, or hot water bottle to the condensate pipe. Just make sure you don’t use boiling water as this can damage the pipe.

Once you’ve thawed the condensate pipe, you may need to reset your boiler to get the hot water flowing again. However, some boilers do this automatically.

9. Boiler Doesn’t Respond To Thermostat

The last of our common boiler problems is also one of the most annoying – when your boiler won’t respond to your thermostat. The good news is that this often has a fairly simple cause and is usually easy to resolve.

How to fix it

  • Battery issues: The most common cause of this issue is weak or dead batteries in your thermostat. If this is the case, all you need to do is replace them and hopefully it’ll start working again.
  • Location: If your thermostat is in an area that’s exposed to heat sources or a poorly insulated area, this can cause inaccurate temperature readings. This means the boiler may not respond as the thermostat is already telling it that a room is at a certain temperature. Try moving your thermostat to a different location. To learn all about the best places for a thermostat, check out our guide!
  • Faulty thermostat: If neither of the above fixes works, you may need to contact the manufacturer for advice or to request a new thermostat.

How Much Does It Cost To Get A Boiler Repaired?

The cost of boiler repairs in the UK varies depending on the type of issue, the boiler model, and numerous other factors. However, the average price of boiler repair bills is around £100 to £500, and an average of £410 for emergency repairs.

How To Prevent These Common Issues

Of course, the best way to deal with any of these issues is to prevent them from happening in the first place. Here are some ways you can do that:

  • Annual servicing: You probably know it needs servicing, but how often should a boiler be serviced? Well, it needs to be serviced annually by a Gas Safe registered engineer to reduce the risk of any of the issues on our list occurring.
  • Maintenance: Regular boiler maintenance is essential to keep your boiler running safely and efficiently. This includes things like insulating every condensate pipe outside your home to avoid freezing and frequently inspecting the pressure gauge.


What boiler problems could cause a home evacuation?

Fortunately, most common boiler issues aren’t dangerous. Yet, if you experience any of the following things, evacuate your home immediately:

  • If there’s a strong smell of gas, evacuate your home and open all of the doors and windows as you leave. Don’t use any electrical appliances or light switches.
  • If you notice sparks or flames coming from your boiler, evacuate immediately and call the fire service.
  • If you or anyone in your home experiences symptoms of carbon monoxide poisoning, such as dizziness, headaches, or nausea, evacuate your home and seek medical attention.

How long should my boiler last?

As long as your boiler is regularly maintained and serviced, it should last for around 15 years before it needs to be replaced. This can vary depending on the model and the type of boiler.

If I don’t use my central heating during summer, will it cause boiler issues?

No, it’s fine to keep your central heating turned off over the summer and only use your boiler for hot water. Modern boilers are designed to deal with periods of inactivity and your boiler should work properly once you start using the heating again.

Final Thoughts

In most cases, the best way to resolve common boiler problems is to call a Gas Safe registered engineer to resolve the issue for you. This is the safest way to handle the problem and a professional can ensure that any necessary repairs are carried out properly.

Still, there are certain minor issues that you can handle yourself, such as frozen condensate pipes and unresponsive thermostats. Remember, the best way to avoid all of the problems on this list is to schedule an annual boiler service.

If your boiler problems persist and you need a new boiler, contact Eco Happy for a boiler quote.

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