Common Boiler Problems and solutions

(Troubleshooting Guide):


The truth is that boiler problems do occur. Sometimes , the issue is preventable but sometimes it’s not. Even if you’ve managed to keep your boiler in good condition, it’s not always going to fail you.

We often don’t fully understand the boilers until there’s a problem and then it dawn on us how awful living in cold temperatures and without hot water is.

However, regardless of the kind or model of boiler you own the fact is that many boiler issues can be avoided with regular maintenance and annual service. Be assured that if your boiler is still in warranty, assistance is too far away.

Surprisingly as per Which? 1 in 5 boilers break down every year. Yep, 1 in 5. That’s quite a bit.


In this guide to troubleshooting boilers we will look at the 12 most frequently encountered boiler issues and solutions. in the event that none of these solutions work, you could always think about the possibility of a upgrade to a new model of boiler.

You might find interesting our tutorial on DIY boiler inspections that you can carry out before calling an gas Safe Engineer.

boiler problems, hot water but no heating, no heating or hot water, low boiler pressure, boiler leaking


Top 12 (most frequent) boiler issues:

  • 1 Boiler Leaking
  • 2 Low Boiler Pressure
  • 3 Boiler Kettling/Noisy Boiler
  • 4 No Heating or Hot Water
  • 5 Radiator Faults
  • 6 Frozen Condensate Pipe
  • 7 Boiler Not Responding To Thermostat
  • 8 Hot Water Doesn’t Work Heating Does?
  • 9 Pilot Light Keeps Turning Off
  • 10 No Power to Boiler
  • 11 Hot Water But No Heating
  • 12 Boiler Not Heating Hot Water Enough


Note If you own an older boiler that is not under warranty anymore You might want to think about a new boiler replacement.

1. Boiler Leaking

A boiler leak is typically an issue that is minor and caused by small holes in the pipework as well being a result of broken seals, or valves. It is often due to the pressure being excessive.

But, in some instances, the leak of a boiler could be a sign of greater issue such as serious corrosion of an internal component like the heat exchanger.


Here are a few of most frequently encountered problems which can lead to leaks. be sure to check our comprehensive guide on boiler leaks for a deeper analysis.

  • Pipework that is poorly installed or corroded.
  • Issue with pressure (too too).
  • Leaky or defective heating exchanger.
  • Leaks are caused by leaks in seals or inside components.
  • What can you do? In the end, you must seek out an authorized Gas Safe Engineer to investigate the problem and take care of anyboiler repair
  • .
    If the leak is due to substantial corrosion, specifically to critical components like the PCB or heat exchanger, be prepared to cover massive repair costs.
    In general, they can cost anywhere from PS400 and PS500. If the boiler you have is outdated and not protected by a warranty, it could be more financially sensible to have new boilers installed.
    If you have recently discovered that you’ve got an condemned boiler, it could be an unpleasant experience If you’re thinking about what you should do, you can refer to our article on when you should change or fix your boiler..


2 Low pressure in the boiler

Your boiler depends on a pressure that is optimal to ensure the water flow throughout the entire system.

If the pressure drops to low, it’s typical for the boiler to shut down and display a low pressure error message. It is common to spot low pressure by taking a look at the gauge.

Your boiler depends on a high pressure to ensure the flow of water through the entire system.

If the pressure drops to low, it’s common for the boiler to shut down and display a low pressure error message. It is usually possible to detect low pressure by taking a look at the gauge.

Low pressure in boilers could be the result of leaks within the system, most often around the pipes’ bends where you can find leaky joint seals and joints. Leaks caused by holes inside important boiler components can cause a loss of pressure, often due to corrosion.

If you notice what may be a sign of an issue, do not try opening the boiler on your own and seek the advice of an Gas Safe Engineer.

If there’s no sign of a leak, then you can consider to increase the pressure of your boiler yourself. It’s something that is relatively simple to accomplish.

Related to: What should the boiler’s pressure be when heating is turned on?

Are you curious to find out which boiler manufacturer did the worst? Find out in our analysis of the most dangerous boilers.

3 Boiler Kettling/Noisy Boiler


Rapid changes in the kinds of sounds generated by your boiler could be an indication of an issue with the boiler.

The buildup of limescale may be a frequent reason for noisy boilers. If limescale deposits accumulate in the exchanger they get excessively heated which results in the formation bubbles and steam creating a familiar whistling sound known as the kettling.

Luckily, these problems are able to be addressed quickly with regular boiler maintenance, or as and when they arise.

In your annual maintenance or if needed the engineer will cleanse your system using high pressure and chemicals to increase the quality of your water and include a limescale inhibitor to reduce the accumulation minerals.

Does your boiler make a distinct sound? Find out the reason with the guide to noisy boilers. guide.

PS If you notice gas smells coming from your boiler, it is an emergency situation and you should dial immediately the Emergency Gas number (0800 111 9999) immediately.

4 No Heating or Hot Water

There are a variety of problems that can lead to an unreliable boiler that is not boiling water or heating, and suffers the complete “lockout”.

This could be due to a malfunctioning pilot light as well as frozen pipes or an defective diverter valve or thermostat issue, and perhaps a problem with boiler’s pressure.

There could be a myriad of underlying problems that can lead to an unreliable boiler that is the boiler without boiling water or heating, and suffers the complete “lockout”.

It could include a defective pilot light as well as frozen pipes as well as an malfunctioning diverter valve or thermostat issue, and perhaps a problem with boiler’s pressure.

When your heating isn’t able to turn on, the most important step is to determine if it is because of the pressure. This can be done by checking the pressure gauge. If it’s below 1 and is not within of the norm (typically green in color) there could be a problem with the pressure.

When the boiler’s pressure appears to be not normal and there isn’t any apparent reason, you’ll be required to contact the the manufacturer of your boiler for assistance.

If there is a problem with the diaphragm, diverter valve or other internal part must be examined and, if necessary, fixed by a registered engineer, a Gas Safe Engineer. They can help you fix the issue.

Are you interested in learning more how to stay ahead of the heating industry in the UK? Explore the latest innovations in hydrocarbon boilers.

5 Radiator Faults

Are you finding that certain radiators aren’t at the temperature they did in the past? Radiators that have cold temperatures at their bottom or with areas of cold and uneven distribution heat usually result from the accumulation of too much air inside the radiators or as a result of sludge accumulation.

A lot of air in your radiators is easily resolved by the process of bleeding the radiators. It’s a easy process, though it can be messy.

But, if, after bleeding your radiators, the issue persists then the cause is probably sludge. Over time , dirt and rust naturally accumulate within the heated water until eventually, the formation of the brown, thick substance referred to as sludge appears.

Sludge can be removed through a chemical flush or a more vigorous pressure flush. It is basically a process that involves the power of high-pressure and mixture of chemicals these flushes provide your boiler and heating system an extensive clean. They also help to get rid of sludge and residues.

Find out all you can about combi boilers by reading our What is an co-boiler guide.

6 Frozen Condensate Pipe

Condensate pipes are responsible for removal of the acidic waste from the boiler and to the outside drains. In winter, which is the coldest time in the course of the year it’s quite common for the condensate pipe to become frozen, which may cause the boiler to shut out.

Usually, when this occurs, an appropriate fault code is displayed on the boiler’s interface, indicating that the condensate pipeline is frozen.

It’s a regular occurrence when the condensate pipe is placed on the outside of the house, where it’s exposed to lower temperatures, and thus more susceptible to freeze.

Most of the time, this problem can be solved easily by freezing the pipe’s contents. To prevent the issue for the long-term it is a great idea to protect your pipe and, if it’s installed outside hiring an engineer to move the pipe. Ideally, the pipe is able to span the interior space of your home in the maximum extent that is feasible.

Have a problem regarding the performance of your Potterton boiler? Learn more about our in-depth guide on Potterton Boiler Problems or, if you’re using an Vaillant and you are experiencing the F28 code, you can read our complete guide to Vaillant F28. Vaillant F28 code.

7 Boiler Not Responding To Thermostat

Most people manage the heating schedule of their boiler and its temperature by thermostats. thermostat So if your boiler ceases to respond to thermostat control, it could cause a significant disturbances.

What could cause an issue with syncing thermostats?

First, you should do the easy things: make sure the batteries don’t need replacing and ensure that you are synchronized with the current time, if clocks have changed recently.

If your boiler is not showing any response, it is recommended to seek out the thermostat manufacturer to seek assistance.

Do you notice that your Worcester boiler show an error message? Find out what that signifies in our extensive Worcester error code guide.

8 Hot Water Doesn’t Work But Heating Does


This problem with boilers is typical in older boilers which have experienced lots of usage and a lot of wear and wear and tear. The most common cause is the defective filter valve.

The diverter valve’s purpose is to divert hot water from the outlets e.g. showers and taps, and to the heating system centrally.

For instance, when you turn the hot water faucets on the valve will close the valve to allow the heating to take place then, when you shut them off, the valve will open up and allow water to flow to radiators.

Diverter valves that are old can become stuck which means that the valve could get stuck, leading to cold or lukewarm water. We have a complete guide on defective diverter valves as well as get ideas on how to solve the problem.

However, the replacement of the diverter valve is a significant expense with an average cost of between PS400 and PS500. If your boiler is old and the warranty is expired, it could be more financially sensible to have your boiler replaced.

Find a astronomically low cost for the new boiler right here.

9 Pilot Light Keeps Going Out

Older boilers don’t have electronic ignition. Therefore, they it is necessary to keep the ignition on to light the fuel in the chamber of combustion. If the ignition continues to turn off, you could have an issue with your boiler.

It could be due to an issue with the thermocouple that is causing it to shut off the supply of gas or a draught entering the boiler and extinguishing the flame. Another problem that can be found is the accumulation of carbon that are deposited on the pilot light that may require to be cleared away.

In the end, because the pilot is intrinsically tied in the flow of natural gas it is recommended that you seek out the assistance of a Gas Safe registered Engineer who is competent to inspect the issue, and diagnose and fix it. problem with the pilot light.

10 Boiler Won’t Turn On (No Power)

When your boiler doesn’t start due to no power for the boiler The issue is likely to be an electrical issue.

The first step is to confirm that the issue isn’t related to your boiler only by examining all the other appliances within your home. If they appear to be functioning, but it’s only your boiler, it’s most likely to be a boiler issue.

A boiler that isn’t functioning will be due with the PCB (circuit board) which could be damaged and require replacement or repair. However, this isn’t affordable and typically will cost around a hundred or so pounds just for the parts. Find our complete guide to boiler PCB problems.

11 Hot Water But No Heating

If you notice that the hot water in your home is working however your central heating isn’t i.e. your radiators don’t seem to be warming it is most likely caused by your boiler’s settings or possibly a defective diverter valve.

The first thing you should do is check the settings of your radiator – make sure that the thermostatic valves don’t have been shut.

Also, be sure to check your boiler’s settings, and make sure that the central heating is on. This will differ dependent on the boiler model However, in most cases there is an option to turn off heating.

If none of these solutions work you’re likely due to the boiler’s malfunction or broken component, which is most likely the diverter valve is defective. Check out our complete guide on the problem with diverter valves.

12 Boiler Not Heating Water Enough

If you’re noticing that the water coming from your hot taps isn’t hot enough and isn’t getting any hotter, then you might be suffering from a boiler issue. The issue could be more severe if it’s affecting the radiators as well.

It could be due to an issue with the boiler’s components, and typically this could be due to a malfunctioning thermostat, a damaged heat exchanger or diverter valve.

One possible DIY solution is to switch the heating on, and then check whether the water coming from your taps is more hot. If you discover that your radiators operate normally, but aren’t getting warm when the water is running, then you might have to change the thermistor in your hot water.

The greatest benefit of this is that it’s an inexpensive component, making it the ideal starting point for the process of troubleshooting your boiler.

If this doesn’t work, it is the following step to seek help of a Gas Safe Engineer who is competent to conduct further investigation, determine the issue and fix the boiler swiftly.

In the end, if your boiler isn’t working and isn’t turning on, it could be due to various issues. It is the only method to figure out the source of the issue is to get a registered Gas Safe Engineer take a check.

If it’s the PCB which needs to be replaced and the boiler is no longer covered by warranty, it may make more sense financially to purchase the boiler replaced instead of a replacement PCB.

A boiler that’s which is no longer covered by warranty could face more problems and need more costly repairs. So why should you purchase an expensive part of an appliance that is likely to be in the process of being replaced?

For the best price on a brand new combi boiler, simply answer a few simple on-line inquiries and we’ll send you an immediate fixed cost.


  • Boilers may face a myriad of problems, and the majority require the intervention of an experienced boiler engineer.
  • Boiler leaks need to be treated as a major issue and addressed as soon as it is.
  • Insufficient central heating could indicate that radiators require bleeding.
  • Low pressure in boilers is often caused by leaks, and is easily fixed by opening the loop for filling.
  • Boiler kettling may cause lots of noise and often requires the system to be cleaned or for an element to be replaced.
  • Condensate pipes frozen in the freezer are able to be removed by using warm water.
  • The boiler might not be responsive to thermostats if that thermostat is not powered by a battery or is far enough from the boiler.
  • The absence of hot water or central heating is typically an issue that requires the assistance of an engineer who works on boilers.
  • If a boiler continues to switch off the engineer will be in a position to determine if an element needs replacement or if the whole boiler must be replaced. Sometimes, this is economical.
  • Boilers can produce a variety of strange and disorienting sounds including gurgling and singing.
  • Do not attempt to repair any part yourself. A professional engineer should solve any problems safely.


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