Top 8 Reasons For A Broken Boiler

Is your boiler broken or not working? Sometimes it's difficult to know if a boiler needs a fix or replacing.

Modern boilers are considered to be resilient appliances and can provide heating and hot water to a home for years.

But, all boilers feature advanced technology and complicated processes, which means that a boiler can encounter problems from time to time. Here’s a list of the possible reasons why your boiler is broken or not functioning properly.

Reasons for a Broken Boiler

  1. Broken Diverter Valve

A diverter valve is used to control the flow of hot water in the heating system. It opens and closes to control the flow between your hot water and radiators. It’s designed to prioritise heating your hot water over your heating system.

A broken diverter valve is likely to cause your heating system to stop working properly. Here’s some signs to look out for if your diverter valve has become faulty:

  • The water is only hot when the heating is turned on.
  • The water temperature from all taps in the house can only reach luke warm temperatures


  1. Kettling

When hearing a rumbling sound or sound like a boiling kettle coming from your boiler can be quite alarming.

However, Kettling does not necessarily indicate a boiler is broken and can be easily rectified. A boiler begins to kettle when lime scale deposits build up on the heat exchanger. A heat exchanger is necessary to heat the hot water. So, when lime scale deposits heat as the water heats the salts become insoluble.

These insoluble deposits can restrict the flow of water and cause the heat exchanger to become too hot and steam. This and the heat exchanger expanding causes the kittling sound coming from your boiler.

The solutions for this problem are straight forward for your gas engineer. It can range from giving the system a flush to replacing the heat exchange or fitting a magnetic and electrolytic scale inhibitor.


  1. Airlocks

Airlocks in boiler systems are common and disrupt the flow of water within the internal plumbing system.

It will prevent the flow of water coming out of the affected tap and also cause all or some of your radiators to heat.

The good news is that airlocks can be fixed through DIY methods.

If your problem is no water coming through the taps then we recommend you try this DIY method:

  • fix a hose pipe to the hot and cold water taps.
  • Once they are sealed and secured on the taps, turn the cold water tap on.
  • The water flowing into the hot water tap will remove any airlock in the system.

If your problem is the radiators are not heating then we recommend you try bleeding the radiators:

  • You will need a radiator bleed key and a towel or old rag to mop up any drips from the valve.
  • Turn off your heating to avoid a lot of water gushing out.
  • Gently turn the key and open the valve until you hear a hissing sound.
  • Shut the valve when the hissing sound subsides this indicates water is coming back through the system.
  • Check the pressure on the boiler before turning the system back on. You may need to increase the pressure on the boiler after bleeding.


  1. Dripping or Leaking

Dripping or leaking can also result in your boiler system not working properly, or breaking down altogether. This can be caused by a range of issues with the boiler system. We have identified some common causes that can cause your boiler to leak or drip:

  • Pipe or part corrosion – Over time pipes, valves can corrode and weaken. It maybe that a particular pipe, valve or boiler part can be replaced. If the corrosion has spread too far and affects too many areas it might be time to think about replacing your boiler.
  • Joints loosen over time – As we’ve explained and mentioned previously in this article pipes can heat and cool. This causes pipes to expand when hot and contract when cooling. This process over time can cause joints to loosen and water to seap through any gaps.
  • Boiler pressure too high – If the pressure of your boiler is too high then your boiler could lead water. This is simply your boiler trying to relieve pressure. So, give your boiler some pressure relief and reduce until your guage meter is between 1 and 2. (Also, see point 8 below for more information on boiler pressure control.)
  • Pump seals have weakened – If your seals around your pump are not doing its job correctly then leaks will occur. Either the seals or pump will need replacing if the problem persists.
  • Poor boiler installation – If the boiler hasn’t been installed correctly and the pipes fitted securely then inevitably leaks and other issues will occur. Only get a gas safe engineer to install a boiler and inspect any issues.


  1. Boiler Pilot Light Gone Out

A common issue on gas boilers is that the boiler pilot light has gone out.

The pilot light is simply a flame that needs to ignite to deliver heat and hot water.

Gas boilers can be stored in cupboards or areas that are susceptible to drafts which can cause the flame to blow out.

It can be fixed by simply re-igntiting the flame. Depending on your boiler model will depend on what mechanism it has to re-ignite the flame.

If re-ingtiion of the flame does not work or it becomes a persistent problem then contact a gas safe engineer for closer inspection.


  1. Pipes Freezing

An issue you need to be prepared for in winter months.

Condensate pipes can freeze if they’re located outside. When this happens, it blocks the water inside as a consequence.

Fortunately, most modern boiler systems have special triggers that switch off the boiler when the water reaches a certain point to avoid any further damage to the boiler.

To prevent pipes from freezing, place thermal sleeves over the pipes particularly if they are accessible from the outside.

If you suspect your pipes have frozen you can pour warm water over the pipes until the frozen water has melted.


  1. Malfunctioning Boiler Thermostat

As is the case with many older boiler systems, the thermostat is usually one of the first components of a home’s heating system to break down and malfunction.

The older the thermostat gets the less efficient it becomes in giving a precise reading of the temperature of the boiler.

This may lead to the boiler system turning the heating off or on by itself, due to the thermostat’s misreading of the temperature levels of the home.

In this case, it would be best to invest in a new thermostat that’s probably more energy efficient.


  1. Pressure Build-up Or Loss

One of the main indicators of this problem is that the boiler starts making gurgling or banging noises, due to either a build-up of air in the system or low pressure.

If the pressure is too high your boiler wont’t be able to thoroughly heat the water. It will also put internal parts under pressure and cause leaks.

If the pressure is too low then it will result in low amounts of water running through your boiler. This will cause insufficient water to flow through the system and not produce enough hot water.

The lack of water can reduce the pressure through taps and showers and water or heating being luke warm.

It’s easy to check if your boiler pressure is too low or high by checking the pressure guage. They are located on the boiler and should read between 1 and 2 (although refer to your boiler make and model specifications for pressure guidelines).

If your boiler persistently experiences high or low pressure then contact a gas safe engineer to check any further underlying issues.

How to Prevent Your Boiler From Breaking Down

The best way to keep your boiler from breaking down unexpectedly is to keep it properly maintained all through the year.

You can do this by having your boiler system regularly checked and serviced by qualified boiler technicians.

This will ensure that your boiler is able to perform at optimum levels at all times and decrease the chances of it breaking down.

Having to replace parts and pay for fixes can be costly and it might come to stage where you have to think about is it worth fixing or getting a new boiler.


What to Do if You Suspect Your Boiler is Broken

If you’re boiler has broken down and you’re beginning to think that replacing your boiler is the best option, then start by research the options here.

If you have a boiler brand or type in mind then we have information on each brand with our boiler search tool.

We always recommend doing your research as we appreciate that replacing your boiler can be a hefty investment. You need to research the various boiler brands, types and payment options. If you want to find out how much money you could save with us then take a look at the boiler savings calculator.

We also understand this research process can be a headache!

So, if you have a broken boiler or seek to replace your old boiler receive let us take the headache away.

Our friendly team will help you understand all the options available to you. And you can even request Hassle Free Boiler quote on any of our wide range of leading brands.

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