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What Is The Biggest Cause Of Boiler Breakdown

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  • Boiler Breakdown, Leaking Boiler, Boiler Problems
  • Posted date:
  • 12-08-2022
What Is The Biggest Cause Of Boiler Breakdown

Have you ever wondered: what is the biggest cause of boiler breakdown? We look at common causes of boiler breakdown and common boiler problems  to watch out for. 

Complete boiler breakdowns and rising energy bills are two of the worst nightmares for homeowners.

While there is never a good time for a new boiler replacement, you can pre-empt getting a boiler installed by looking out for the following problems we're addressing in this article.

What Is The Biggest Cause Of Boiler Breakdown?

Unless you want cold showers throughout winter and cold weather, you should take good care of your central heating systems and boiler. Many leading models have a built-in pressure gauge, meaning you can check the boiler pressure to help it function properly at all times.

A domestic hot water boiler's standard wear and tear are why many are experiencing boiler breakdown, especially in older boilers. Due to the many internal components at play for a boiler to work (the pressure valve, pump seal, diverter valve and gas supply, among many more), you should always consult a Gas Safe registered engineer to conduct work and repairs.

Due to the nature of a gas boiler, or any gas appliance, a heating engineer can perform boiler repair without causing potential harm to you and your property.

Common Causes Of Boiler Breakdown

Many boiler components will break and wear down over time, typically through no fault of your own. As you rely on the unit for heating and hot water, it's common for the boiler's pressure and water flow to suffer due to a build-up of sludge, rust and air.

These factors can cause an inefficient boiler overnight and your energy bills to increase substantially as you attempt to rectify the issue.

To avoid a broken boiler and paying for boiler engineers to visit your property, here are the most common breakdown issues:

What Is The Biggest Cause Of Boiler Breakdown?

Age Of Boiler

Older boilers over ten years are more likely to experience a boiler breakdown as rust and limescale build-up affects overall performance. You will also require replacement parts as corrosion and sludge affect electrical components. This regularity can vary depending on how often you care for and maintain your boiler.

It's common for dirt, dust, and debris to affect water flow and stop enough hot water from circulating throughout the system. If you are experiencing any unusual boiler noises, a boiler leak or low boiler pressure, you will significantly benefit from a gas-safe engineer visiting your property.

In most cases, a professional engineer can locate the fault, a component or part replaced, and the boiler can continue providing heating or hot water. If it does stop working entirely, you may need a new boiler installed.

Frozen External Pipes

Frozen condensate pipes are a common occurrence, especially during the winter months when the temperature drops. This pipe is responsible for transporting acidic water from your boiler to your external drain, which can quickly freeze over in colder climates or areas without proper ventilation.

During the warmer months of the year, these pipes can remain inactive, and the strain from transporting this water from one temperature to another can cause more issues. If you notice a gurgling sound from your boiler or are experiencing no heating or hot water, you may be suffering from this issue.

You can help defrost and thaw the pipes when you pour hot water (not boiling water) over them. Leaving these untreated can lead to burst pipes, causing far worse issues.

Faulty Diverter Valve

Diverter valves are present on combi boilers, which are opened and closed depending on whether heating or hot water is required. You may not receive heating with a faulty diverter valve, or the boiler isn't working properly at all. 

If you have fixed the diverter valve, but the boiler problems continue, you may have excess sludge levels in the radiators at your property. If so, you will notice cold patches along the radiators, perhaps only the bottom half.

This common boiler problem can be fixed with an engineer conducting a power flush of your heating system.

Damaged Pump Or Pump Seal

Another common cause of boiler breakdown is a faulty boiler pump. This can result in sludge, jammed propellers, or leaking. If you notice leaking, strange noises coming from your boiler, or general unresponsiveness, this is a sign of a broken internal component, most likely a damaged pump seal.

While there may be some possible fixes to conduct yourself, you should contact a professional gas-safe engineer if you do not feel comfortable working on your boiler. Many gas suppliers and boiler manufacturers do not allow you to work on your own boiler, meaning you must call a heating engineer.

Check your boiler manual for more information if you are concerned.

Low Water Pressure

Low pressure on your boiler is a sign of either water leaks or recently bled radiators. Before panicking, you should check the pressure gauge for a reading.

Anything below 1 means your heating won't work correctly, and your house won't reach the desired temperature. If you rectify the issue, but it continues, you may have a faulty pressure relief valve on your hands. If your boiler does not provide heat as desired, this is a likely reason.

In such instances, call a gas safe engineer, and they can assess for a leak or simply repressurise your boiler for you if you do not feel comfortable.

Thermostat Malfunctions

Some of the most common boiler problems arise from your thermostat not working. If you have a boiler that works via a smart thermostat, you must ensure the device is working, or you will receive no warmth. If the temperature settings are set to the wrong time or date, the boiler will not cooperate with you when you want it to.

If the boiler cannot accurately communicate with the thermostat, it will not know when to switch it on and what the desired temperature is.

A simple fix is replacing the batteries, cleaning the thermostat, and checking all the settings are programmed correctly.


Limescale is common throughout many areas of the UK where hard water is present. If limescale builds up, the water supply will be blocked and restricted. This causes the water to overheat and boil, resulting in your boiler "kettling".

If you notice any unusual noises from your boiler, very akin to a boiling kettle, you will need a Gas Safe heating engineer to perform a power flush on your central heating system.

This will wash out any limescale but consider investing in scale reducers and water softeners in the future.

Thermocouple Malfunction

Older boilers will experience this more than modern models, as they ignite electronically. If your pilot light continues to go out, the gas valve safety device (thermocouple) could malfunction or be faulty.

Pilot lights serve as the ignition source for gas boilers and are required for older boilers to work and provide heat. If you are noticing an error code or other warning signs on your boiler, this is also a sign that the thermocouple needs replacing.

Regular cleaning and maintenance of the thermocouple should prevent it from happening again in the future.

Common boiler problems

Thankfully, most common boiler issues have a simple fix once you know what you're looking for. If your heating or hot water has been compromised, or you're noticing strange noises from the pipework, there may be a fault in the central heating system.

In most cases, annual servicing is the best way to keep your boiler in good health, especially combined with general maintenance. 

Common Boiler Problems

Hot Water But No Heating

As your boiler is supposed to provide hot water from taps and heating, if you notice only hot water - this is a problem. One of the most common causes of your heating not switching on at the desired time is the thermostat being set to the wrong date and time.

The boiler pressure may also be incorrect, meaning the boiler will not work effectively. Both solutions are simple for most homeowners; changing the thermostat batteries or repressurising the boiler. Unfortunately, if you fix both of those problems and the heating remains vacant, this signifies a deeper issue.

Broken diaphragms, failed motorised valves, and airlocks can also be causes in many combi boilers. The director valve could be faulty or damaged, meaning the boiler's efforts are not being channelled to the heating and only the hot water. As with all of these problems, always contact a professional if you are unsure.

No Heat Or Hot Water

When your boiler is not providing heat or hot water to your home, that is a cause for concern. The first thing you should do is check the power supply, ensuring the boiler is receiving the necessary power. Many modern boilers are installed with the ability to display an error code, so check that for more information.

From there, check that you are receiving gas from your gas supplier and ensure your oil tank has sufficient levels. You could also be suffering from a frozen condensate pipe, as addressed above.

Boiler Is Leaking

Boiler leaks are never a good sign and should be treated seriously. This signifies a broken internal component, such as the pressure valve or pump seal. Your boiler could be too high, causing the valve not to work, or the seal is broken and damaged, causing a leak.

When you notice the leak around the boiler tank itself or the pipes, this is more likely going to be caused by corrosion. Regardless, contact a professional engineer as soon as you can to rectify the problem.

Boiler Is Kettling

Limescale can build up inside the pipes and around the boiler's heat exchanger, causing a kettling noise to erupt from your boiler. This heat exchanger is responsible for transferring heat from the fuel to the water, eventually circulating around the entire heating system.

When you leave this untreated, your boiler will cost more to run and can actually shorten the unit's overall lifespan.

Low Boiler Pressure

As we've mentioned above, low boiler pressure is a common problem that can cause your boiler not to work effectively. Your water pressure is a measurement of the hot water passing through the central heating system, which must be balanced perfectly.

When this pressure drops to a low value, your heating will not work. The pressure gauge on your boiler will show the current value, with a red zone you should avoid as high pressure is also worrying.

If the water pressure drops below 1, you need to repressurise the boiler.

Radiators Are Cold

Cold patches on your radiators are a sign of sludge, limescale and rust building up inside the system, limiting the flow of hot water. If only the bottom of your radiator is cold, you can sometimes fix this by bleeding it. If all your radiators are connected to the same boiler, but only some are warming up, they could need balancing.

This process involves checking all the valves on individual radiators, which can make the problem lessen. However, a professional can perform a power flush, which you should absolutely receive if you never have before.

Boiler Keeps Switching Off

When you notice your boiler switching off repeatedly, without you doing anything, this signifies many possible things. Thermostatic issues could be the most possible, with the thermostat reading the wrong time, so the boiler switches off too early.

There could be a lack of water travelling throughout the system due to a closed valve. Sludge, debris and air can get trapped in the central heating system and cause problems, which is why you require regular heating maintenance.

If you ever notice something wrong with your gas boiler or other appliances, don't hesitate to call a professional, especially during the colder seasons of the year. You shouldn't have to live without hot water and heating, so let a professional fix the issue.

Do you require radiator and heating servicing? We offer services to both domestic and commercial customers Uppingham, Oakham, Stamford and Rutland. Our charges are highly competitive and realistic. If you are experiencing problems with your central heating - Please contact us.