10 Common Boiler Problems: How to Fix Them?

Oscar Garner

By Oscar Garner

Last Updated on July, 2024

Whether the hot water stops working in the shower or you notice your breath misting up in front of your face in your living room, a broken boiler always leads to a moment of utter terror. 

Boiler repair bills weren’t part of the plan this month. A new boiler? That wasn’t part of the plan this year! 

Well, take a breath. Boilers are susceptible to many issues, but not all require you to call a Gas Safe Registered Engineer or rethink your budget. 

Sometimes, a little thinking and determination will warm you up again in a jiff. 

We’ll walk you through some common boiler issues to help you determine which ones you can handle and which are better left to the professionals. 

Quick Summary

  • Common boiler problems include no hot water or heating, frozen condensate pipes, low boiler pressure, leaks, faulty thermostat, pilot light not working, kettling, and radiators not working.
  • Boilers are susceptible to many issues, some can be fixed by homeowners, while others require a professional.
  • Annual maintenance and routine checks can help prevent major boiler issues. When in doubt, it is best to call a registered engineer for assistance. The biggest cause of boiler breakdowns can vary, but some common causes include high corrosion levels, low water pressure, or faulty components such as a thermocouple or diverter valve.

10 Common Boiler Issues (And How to Fix Them?)

Hot Water, But No Heating 

a plumber fixing a water boiler

This is not a total loss; you can still enjoy a hot shower anytime. However, unless you plan to set up camp beneath your showerhead, you must do something about the heating. 

Functioning hot water with a non-functioning heating system often happens when your boiler is not set to the correct settings. Another reason could be that your boiler’s pressure has dropped too low, causing your central heating system to stop working. 

If you own an older combi boiler, the culprit could be a faulty diverter valve. This valve diverts water heated by the combi boiler to the radiators and taps in your home.

Over time, they can become clogged with dirt and debris from the water supply or succumb to wear and tear. When this happens, the diverter valve will get stuck and stop supplying heat to your radiators.

How to Fix it?

Most combi boilers have separate controls for radiators and hot water, so ensure that both are turned on. You should also check your thermostat settings and whether your timer has been set to turn the heating on at another time. 

Next, check the boiler’s pressure gauge. If the dial reads below 1, you’ve got a low-pressure problem, and we recommend calling the manufacturer for assistance. 

If it’s not the settings or the water pressure, the issue is probably your diverter valve. You’ll need to call a service engineer to take a look. 

A Gas Safe Engineer will diagnose the problem and perform a chemical flush to fix it in case of a clog. Depending on the damage, they may advise that you replace the component altogether.

No Hot Water or Heating

Talk about double trouble! 

There are several reasons why your hot water and central heating system might stop working. The simplest explanation is that your boiler has lost an essential supply, be it power, gas supply, or fuel, depending on the type of boiler you have. 

If your thermostat is set to the wrong settings, your radiators and hot water could also cease functioning. Luckily, this should be a reasonably easy fix you can do yourself. 

Now, if you’ve used up some of that luck at the pub, watching the Premier League, you could be dealing with a broken or faulty pilot light, a frozen condensate pipe, or boiler pressure issues–which aren’t nearly as easy to fix. 

How to Fix it?

The first thing you should do is ensure that your boiler is receiving power. If you own a gas boiler and have already settled your bill, contact your gas supplier to clarify that you are still receiving gas to your home. If you own an oil boiler, ensure your storage tank has not dried up.

Next, check whether your thermostat is set to a lower setting than the current room temperature. If so, your central heating might have turned itself off when the temperature increased. Set your thermostat to a higher setting and see if that fixes the problem.

You should also check your boiler’s built-in pressure gauge and see whether the dial is below 1. A reading between 1 and 2 typically shows that your pressure level is fine.

If it’s not the temperature or pressure, the issue likely stems from your pilot light or your condensate pipes being frozen. The good news is you can remedy these problems yourself, and we’ll show you how in just a bit. 

However, the issue could also be caused by a broken internal component, such as a diverter valve. In that case, you’ll need the help of a heating engineer–time to get the phonebook out.

Frozen Condensate Pipe

a picture of a Frozen Condensate Pipe in a water boiler

Condensate pipes are the unsung heroes of your heating system. Why? Because they remove the wastewater your boiler produces during the condensing process and transport it to an outside drain. 

Since most condensate pipes are fitted externally, exposure to cold weather causes them (and the acidic water inside) to freeze. When this happens, your boiler will automatically shut off and cut the heating to your house. 

And there’s no worse time to lose the heating or hot water than during winter. Thankfully, there is a way to prevent you and your family from turning into human popsicles…if you’re willing to brave the cold for a few minutes. 

How to Fix it?

First, identify the issue. Your boiler makes this easy by displaying an error code to inform you about a frozen condensate pipe. You may also hear a gurgling noise from your boiler, indicating that the frozen pipe is blocking the water flow. 

Once you identify the issue, locate the condensate pipe to unfreeze it. It will be made of plastic and should be fitted right above a drain outside your house. 

You can defrost it by: 

  • Pouring warm water over the frozen part of the condensate pipe
  • Placing a hot water bottle on the affected area 

This should fix your boiler problem and restore the heating. However, if it doesn’t work or you’re unsure about thawing the condensate pipe yourself, you should call a heating engineer to take a look. 

Low Boiler Pressure 

This is one of the most common boiler problems, especially with modern systems. Low boiler pressure restricts the water circulation in your boiler, causing your central heating and hot water to fail.

Low pressure often happens due to leaks in your system, bleeding radiators, a broken valve, or an issue with your pressure gauge. 

How to Fix it?

First, ensure there are no leaks in your boiler or heating system. You can then open the boiler and check the reading on the pressure gauge. If the dial is below 1, it indicates low water pressure. The boiler may also display a fault code to inform you about the issue. 

Once diagnosed, you can try repressurising the appliance yourself. Make sure to follow the boiler manual or call the manufacturer for assistance.

If the problem persists after the reset, you should contact a Gas Safe Engineer, as you may be dealing with a broken valve or a faulty radiator. Do not attempt to open the boiler if there is visible leaking or dripping. Instead, you should call your Gas Safe Engineer to take care of it. 

Boiler Leak

water boiler auto leak problem

No matter how cold you are from the lack of heating, a leaky boiler is guaranteed to make you sweat. 

There are several reasons why your boiler may start to leak or drip. These could include poor installation, high pressure, a faulty heat exchanger, a damaged internal component like a pump seal or pressure valve, or corrosion over time. 

How to Fix it?

The first step is to determine where the leak is coming from. Once you’ve identified the source of the leak, have a qualified engineer diagnose the problem. You may feel tempted to open your boiler and check for high pressure, but we recommend against it for safety reasons. 

Here’s the bad news: most older boilers start leaking due to high corrosion levels, and fixing them isn’t always worth it.

Repairing a leaky boiler could cost you between £150 and £1,000 in the UK, including parts and labour. So, if your boiler breaks due to a leak and is no longer under warranty, you should consider getting a new boiler installed

Faulty Thermostat

Thermostat issues can manifest in different ways. It might display inaccurate temperature readings or be non-responsive to your temperature settings, resulting in the boiler failing to provide heat to your home when needed. Whatever the case, it can be infuriating to deal with. 

That being said, you can try a couple of things to get your thermostat working again before taking the old sledgehammer to it. 

How to Fix it?

First, ensure that your thermostat is turned on. If your boiler has a smart thermostat, check that your WiFi is functional and try reconnecting it to the network. If your thermostat displays an accurate reading, but your boiler still won’t respond, try reconfiguring the settings.

Ensure you’ve set the timer properly and that your temperature setpoint is higher than the room temperature. On the other hand, if the thermostat reading is inaccurate, you could try replacing the batteries. 

If all else fails and your boiler remains non-responsive to the thermostatic control, it might be time to replace your thermostat. We recommend consulting your manufacturer for a second opinion. 

Pilot Light is Not Working 

a picture of a worcester boiler flashing blue light

While most modern systems utilise an electronic spark generator to provide heating or hot water, older boilers use a pilot light. 

This small blue flame is usually visible at the front of your boiler, though some models may require you to open an interior panel to access it.

The pilot light ignites the gas that enters your boiler. It keeps itself burning by feeding off the gas supply and is a reminder that things are going smoothly. 

So, if your pilot light gets snuffed out or starts flickering, it could indicate problems such as too much air entering your system through the vents, a clogged orifice, or a faulty thermocouple. Just like the pilot light feeds off gas, some of these issues will feed off your wallet. 

How to Fix it?

If you determine that your pilot light went out because of a strong draught, you can safely relight it by following the instructions in your boiler manual. 

However, if this keeps happening even when it’s not particularly windy, you should consult a heating engineer to fix the problem. 

Sometimes, the issue could be the gas supply. Start by checking whether other gas appliances in your house are functional. If so, the culprit might be a broken thermocouple, which cuts off gas to your boiler even if the gas stopcock is turned on. 

Once you’ve confirmed this is the case, the next step is to call an engineer, the only one qualified to tackle such an issue. A clogged orifice – a cap with a small hole that controls the gas flow from the main burner – may also affect your pilot light.

As dirt accumulates in this opening, the flame will grow weaker and change from blue to yellow. When this happens, a professional must perform a cleanup to revive the pilot light. 

Boiler is Making Noise (Kettling)

This is not only one of the most common boiler problems, but it’s also one of the most annoying. Much like an angry two-year-old, a faulty boiler can produce several different noises with different meanings. 

Here are some sounds you are likely to hear from your boiler, along with their causes: 

  • Kettling – usually happens when limescale or debris builds up in your heat exchanger. 
  • Gurgling – occurs when your condensate pipe freezes or becomes blocked with excess air. 
  • Banging – happens when your boiler’s heat exchanger becomes clogged or due to damaged pipework.
  • Whirring – not a concern if the noise is muted, but loud whirring could signal a faulty pump. 
  • Clanging – indicates an issue with the boiler fan or a compromised pipe. 

How to Fix it?

Unusual boiler noise is no small matter and requires prompt attention. Once you properly place the noise, you should get a Gas Safe Engineer to come over and address any issues. 

They may perform a chemical flush, a repair to clean heating systems or install a limescale reducer to protect your boiler from clogs and blockages. 

Faulty Radiator

Sometimes, it’s not the boiler to blame for your chattering teeth but the radiators. Your radiators may take longer than usual to heat up or have cold patches on the bottom. This usually happens when debris builds up inside them. 

Conversely, if only the bottom of a radiator is heating up, it is because too much air is trapped in the radiator’s system. 

You might also find that some radiators in your home are working while others aren’t. This imbalance often occurs due to uneven hot water distribution from your boiler. 

How to Fix it?

If your radiator is only heating up at the bottom, you can fix it through “bleeding.” This is a simple procedure that you can perform without an engineer.

As for unbalanced radiators, you only need to adjust the valves to get them working again. You can contact the manufacturer for assistance. 

If issues remain after bleeding and balancing your radiators, you’re probably dealing with a blockage. In this case, you’ll need the help of a Gas Service Engineer to remove the debris. 

Also, remember that while it’s possible to bleed and balance radiators by yourself, you should only do so if you have done similar repairs in the past. If not, it’s a good idea to call a professional. 

Boiler Keeps Switching Itself Off

a picture of a water boiler kept in the kitchen

No list of common boiler problems would be complete without this little gem. Having your boiler switch itself off for no apparent reason can make you feel like you’re in a sci-fi movie.

However, there are some simple causes behind this problem, and none of them are related to a robot uprising. 

Thermostat issues and low boiler pressure are two of the easier ones to fix. However, your boiler may also power down by itself due to excess airflow, a clog in the heating system, or a closed valve restricting the water flow. 

How to Fix it?

You can confirm low boiler pressure by checking the reading on the pressure gauge. This is usually located behind a panel on the front side of the unit. If the dial is anywhere below 1, it shows that the boiler pressure is below the acceptable level.

Once you’ve confirmed the issue, follow the instructions on your boiler manual to repressurise your boiler. 

You could try changing the thermostat settings if the pressure reading is normal (between 1 and 2). Ensure that you’ve set the thermostat higher than the current room temperature. If not, adjust it and see if that fixes your boiler problem. 

Call a Gas Safe Registered Engineer to diagnose the issue if these measures fail. 

How to Prevent Boiler Issues Before They Happen? 

Few things are worse than abruptly losing the heating or hot water in your home. Boiler problems aren’t just stressful and inconvenient; they might also set you back a hefty sum on repair bills. 

Either that, or you’ll have to begin a side gig as the local blanket thief. While you can’t stop your boiler from having problems, you can certainly reduce the number of times they happen.

Simple things like routinely inspecting the pipes, radiators and boiler pressure level will help you avoid sudden issues in the future. 

Adding insulation to your home will let you retain heat and prevent draughts from entering your heating system.

Perhaps most importantly, you should ensure your boiler gets its annual service. This will keep it in the best possible condition and reduce the likelihood of any serious malfunctions in the next twelve months. 

When Should You Call an Engineer? 

an engineer working on a water boiler

While you might be reluctant to pay a heating engineer to visit your house, the reality is that certain boiler problems require qualified professionals. 

Suppose you’re dealing with broken components like airlocks or motorised valves, clogged radiators, or leaks from your boiler. In such cases, you’ll need the assistance of a Gas Safe Engineer to rectify the situation. 

Not only will they diagnose your issue and perform repairs, but you can also rely on them for a trusted opinion on whether repairs are worth your money in the first place. 

In other words, if a registered engineer thinks it’s time for a new boiler, you should take them at their word. 

Useful guides:


Even with the best maintenance, your boiler is bound to break down sometimes. Think of it as burnout from providing such an essential service to your household. It’s important to know how to get your boiler working again when that happens. 

As we’ve discussed in this article, there are some boiler problems that you can solve by yourself and others that are better left to an engineer. Before doing anything, ensure that you identify the root of the issue. You can then decide whether to roll up your sleeves or call a professional. 

Best of luck! 


A common problem in a boiler is low water pressure.

The biggest cause of boiler breakdown is a lack of regular maintenance.

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