No one wants to have a problem with their boiler but unfortunately, issues can crop up from time to time. Thankfully, most of the issues that occur with modern boilers can be easily resolved by a Gas-Safe registered heating engineer. Sometimes you may even be able to fix the problem yourself by checking the fault code on your boiler.

You can also prevent problems from arising in the first place by ensuring your boiler is serviced regularly. Some faults, however, can arise despite your best efforts. 

Here, we run through the top 10 most common boiler problems.

  1. A leaking boiler
  2. Low pressure
  3. High pressure
  4. No heating/hot water
  5. Hot water works but no heating
  6. A noisy or ‘kettling’ boiler
  7. Boiler won’t ignite
  8. Boiler keeps switching off
  9. Frozen condensate pipe
  10. Pilot light keeps going off (Older boilers only

1. A leaking boiler

Water or gas leaking from a boiler is a sign that something isn’t right. Let’s take a look at what these leaks might mean.


Water leakage can present in a number of ways. Perhaps the walls around your boiler, or the floor underneath it, has become saturated with water or maybe you’ve found staining, mould or damp near your boiler. You might also suspect a leak if your boiler keeps losing pressure despite you topping it up. Whatever the case, the problem should be investigated.

There are a number of reasons why your boiler may be leaking water. Here are some:

  • the boiler pressure is too high
  • the pipes or tanks are corroded
  • the pipes have been poorly installed
  • the joints between the heating system and pipes are badly sealed
  • the boiler is old and has stopped working properly
  • poor maintenance of boiler and system

If you suspect a leak, you should consult a qualified boiler engineer to identify and resolve the problem as soon as possible.


If you think gas is leaking from your boiler, you should open all doors and windows, turn off the gas at the mains tap if it’s safe to do so and leave the property immediately. You should call the Gas Emergency service free of charge on 0800 111 999.

The first sign of a gas leak is usually a pungent smell, which people describe as being like rotten eggs or rotten cabbage.

A gas leak is usually down to a poor connection or fitting that hasn’t been installed or maintained properly or other boiler parts that have suffered wear and tear.

To help prevent gas leaks, you should get your boiler or gas appliance installed and serviced regularly by a Gas-Safe registered engineer. You should also avoid blocking or covering any ventilation grilles, bricks or flues. 

2. Low pressure

There are several things that can happen if your boiler pressure is too low. You may find that:

  • you have no hot water
  • you have no heating
  • your radiators aren’t heating up properly
  • the needle on the pressure gauge drops

Low pressure is usually caused by a water leak in the system. Alternatively, you may come up against this issue after you bleed a radiator. This is because when you do this, you release air, which lowers the pressure in your system.

To find out what action to take if you have this problem, including how to repressurise your system, read our article ‘What to do if your boiler pressure is too low’. 

3. High pressure

As a general rule, if your boiler’s pressure gauge is reading over 1.5 bar when the heating is off or over 2 bar when the heating is on, your boiler pressure is probably too high. However, you should consult your boiler manual to find out the recommended levels for your specific model. Unfortunately, you may only realise there’s a problem with the pressure when your boiler breaks down.

Your boiler’s pressure may be too high for a number of reasons. Here are some:

  • wrongly estimating the pressure when repressurising
  • putting too much water in the system
  • faulty parts - this can be the problem even if your boiler is relatively new
  • an ageing boiler - if your boiler is 10 or so years old and experiencing pressure problems, it may need to be replaced
  • lack of correct maintenance

4. No heating/hot water

If you’ve ever experienced having no hot water or no heating, you’ll know how inconvenient and frustrating it can be, especially during the winter months.

If you have no heating and no hot water, it may be that:

  • your boiler isn’t getting fuel
  • your thermostat is not set correctly
  • you have a frozen condensate pipe
  • the boiler pressure is too low
  • the pilot light has gone out and your boiler won’t ignite (in older boilers)

If the cause isn’t obvious, you may need to call on a trained heating engineer for help identifying and fixing the problem.

5. Hot water works but no heating

If your heating has failed to come on when you expect it to, it’s worth checking the thermostat settings first of all to make sure they’re correct. If they are, you should check your boiler pressure next. Sometimes your heating may stop working due to a drop in boiler pressure. If this is the case, you may be able to repressurise as per the link referenced above.

You may also have a fault that requires specialist attention, such as a problem with a diverter valve. It could also be a problem with the timer or thermostat.

6. A noisy or ‘kettling’ boiler

Your boiler may make a variety of different noises if something isn’t working as it should. This is known as kettling. The type of noise it’s making, from gurgling and whooshing, to clanging and banging, can help you to pinpoint the issue.

The good news is that you may be able to fix this problem without a callout from an engineer. Depending on the exact issue, taking simple steps, such as bleeding the radiators and reducing the pressure, may be enough to resolve the issue.

You may also find that your fan is responsible for the noise. If your fan is making constant noise, at intervals or when the boiler is switched off, it may be a sign that this part of your boiler needs to be replaced. This is especially likely if your fan is old or if it is positioned high up in the boiler as the heat can cause the bearings to dry up. Generally speaking, a faulty or loud fan can’t be fixed and will have to be replaced. 

7. Boiler won’t ignite

When your boiler won’t fire up at all, it’s obvious that something is wrong. There are a range of issues that can cause this problem, including:

  • a tripped fuse
  • faulty gas valves
  • low pressure

With high-tech models, it’s also possible that your boiler won’t ignite simply because your home is already at the correct temperature. There are some practical steps you can take to fix a boiler that won’t ignite. However, it’s likely that you’ll need an engineer to investigate if the cause of the problem isn’t obvious. 

8. Boiler keeps switching off 

It can be very frustrating if your boiler keeps switching itself off for no apparent reason. If this is happening to you, there can be a number of causes, including:

  • Overheating - modern boilers tend to have a safety feature that automatically switches them off when they reach a certain temperature to prevent overheating. Overheating can happen if water isn’t flowing properly due to blockages in the system.
  • Low water pressure - again boilers can switch off automatically to prevent overheating if the water pressure is too low. You can remedy this problem by re-pressurising your appliance.
  • Thermostat issues - if your thermostat is faulty or hasn’t been set to the correct temperature, you may find your boiler shutting itself off when you don’t expect it to. You should check your thermostat settings as a first port of call and if there are no issues, you may need an engineer to check it for faults.
  • Excess air - if there is air in your system, your boiler may shut itself down. You may be able to tell there’s excess air because your pipework and radiators may make noises. To release trapped air, you should bleed your radiators

If you’ve managed to fix the issue, you will need to reset your boiler afterwards. If you’re in any doubt about what’s causing your boiler to switch off, however, you should contact a heating engineer for help. 

9. Frozen condensate pipe

If your boiler has stopped working during a spell of cold weather, it may be due to a frozen condensate pipe. A condensate pipe is a pipe that carries waste water from the heating system into the home’s drainage system. If this pipe is frozen, you may find that your boiler is making a gurgling noise too. Your boiler will stop working as a safety feature. Thankfully, you can usually fix a frozen condensate pipe without professional assistance.

10. Pilot light keeps going off  (Older boilers only)

If you have an older boiler, you’ll probably have a pilot light. This is a small flame that ignites the gas in your boiler, enabling you to have heating and hot water in your home. You can usually see the light through a window in the boiler casing. If your pilot light keeps going out, you may have one of the following issues:

  • A faulty, dirty or misaligned thermocouple - this is the copper rod that is used to detect a flame. It can prevent the pilot light from staying on if it’s broken, unclean or not aligned properly. You will need a heating engineer to determine if this is the cause of the problem.
  • A buildup of dirt - when a pilot light is working correctly, it should be blue in colour. If it’s yellow, it may indicate that dirt and debris have built up in the pilot orifice, stopping the light from igniting. This should be dealt with by a Gas-Safe registered engineer.
  • Draught - if your pilot light tends to go out during windy weather, a draught may be the culprit. If you think this could be the case, you should have your boiler inspected as this shouldn’t be happening.


  • There are many different problems that can cause your boiler to malfunction, most of which can be fixed by a trained heating engineer.
  • Fixing a boiler can lead to accidents and injuries so you should consult a qualified Gas-Safe engineer if basic troubleshooting steps don’t work.
  • If you suspect a gas leak, you should call the Gas Emergency service free of charge on 0800 111 999 immediately.
  • Avoid blocking or covering any ventilation grilles, bricks or flues to prevent gas leaks.
  • Consider getting a carbon monoxide detector fitted in your home.
  • You may be able to resolve low pressure by re-pressurising your system.
  • You may be able to reduce high pressure by bleeding the radiators.
  • A lack of hot water may be caused by a frozen condensate pipe.
  • Preventing limescale buildup can help to prevent boiler kettling.
  • If your boiler won’t turn on, you should check the gas supply and try resetting it. You will likely need a heating engineer to investigate if these steps don’t resolve the issue.
  • Boilers are designed to switch off automatically to prevent overheating. If your boiler keeps switching off, a blockage may be causing an increase in temperature.
  • You can insulate your condensate pipe to reduce the chances of freezing.
  • In older boilers, a pilot light that keeps going out may indicate a problem with the thermocouple, a buildup of dirt or a strong draught.
  • To keep your boiler in good working condition, get it serviced regularly by a Gas-Safe registered heating engineer

Unsure how to choose? Get a no-hassle, free consultation from our experts!

Share this article

Share this article

Most read articles
Latest topics

Looking for a new heating system?

Get your free quote from a local installer