Boiler Servicing: A Complete Guide for Homeowners

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Last updated: October 31, 2023

Your home’s gas boiler plays an essential part in creating a happy home by keeping you warm and well supplied with hot water on demand. Which is why they need the right amount of TLC to keep them reliable, which includes an annual service check.

While a requirement of most boiler warranties, keeping up with your annual service also makes good sense as it can keep your boiler working efficiently and help nip any mechanical issues in the bud, saving you on more expensive repairs.

But what is included in a boiler service and what can you expect? We take a look in our homeowners’ guide to boiler services.

Why Should I Get My Boiler Serviced?

Safety and efficiency are the two overriding reasons why you should always get your annual boiler service. And the cost of boiler service checks will save you money and inconvenience in the long run as well as keep your manufacturer’s warranty happy.

When it comes to safety, you should never take risks with your boiler and so an annual service will check for any problems that if left, could lead to carbon monoxide emissions. This gas has no taste or smell but can cause potentially fatal carbon monoxide poisoning. So, as well as having carbon monoxide detectors in your home, you should always stick to your annual boiler service appointment.

You should also see your annual boiler service as a health check that can keep your boiler working effectively and efficiently and identify any potential issues before they become more serious and costly. This can also help to extend the working life of your boiler and help reduce the need for expensive repairs.

An annual service will keep your warranty valid too, particularly if it has been extended, but any service checks must be completed by a qualified engineer who has been Gas Safe registered. Your engineer can also advise you on how to get the best out of your boiler and keep it working at its efficient best, potentially helping you to save on your energy bills.

What Does a Boiler Service Involve?

A boiler service involves a visual inspection as well as full examination of all the boiler components, which is why only a Gas Safe registered and fully qualified engineer should carry it out. And your engineer should follow a comprehensive service checklist.

Here is what you can expect to be done during your annual boiler service:

  • Location of the boiler – this will include the surrounding environment of your boiler’s location and how it has been installed. The location must be within regulations covering gas meters, appliances, ventilation and proximity to any combustibles.
  • Visual inspection – before opening up your boiler to check on its internal components, the engineer will give the unit a full visual inspection. This is an initial way of assessing the condition of your boiler and identify any immediate issues or damage. The visual inspection will include the external pipework and flue to ensure they have been correctly installed and if there’s any signs of deterioration or leaks.
  • Operation check – next up is a full check of the boiler’s controls and safety functions to see how well the boiler actually performs. The boiler will be fired up and closely observed to see – and potentially hear – any issues there may be in its running. All the controls should be in full working order, the correct safety functions and devices in place and the connections sound. The engineer should also carry out gas tests to check that the pressure levels are appropriate, and the gas is flowing as it should, or if there are any gas leaks. The gas consumption levels should be referenced against the manufacturer’s guidance to ensure the gas rate is compliant. And the final part of the operation check will be test of the boiler’s Emergency Control Valve, or ECV, which is the way to safely shut off the boiler in the case of a serious malfunction.

  • Flue check – the flue is the pipe that runs from your boiler to outside and so needs to be complete and unblocked. Your engineer will do a full check to ensure it is correctly and safely fitted and there are no obstructions in the flue terminals.

  • Internal inspection – once the external visual inspection has been completed, the engineer will open up the boiler to check all the components inside. The first check will be the internal structure to ensure there are no signs of leaking, overheating or corrosion. They will then move on to the main internal boiler parts, which will include the heat exchanger, the main burner, as well as the fan, the flue ways and all the essential seals. While inspecting, then engineer will also clean all the main components and ensure they correctly fitted and working.

If any components are found to be faulty and can’t be repaired, your engineer will recommend replacement parts.

Water system inspection – while inside the boiler, the engineer will also check the water gauge, including water pressure and levels, as well as the PH of the water and check for limescale and sludge which may damage components and be compromise the boiler’s efficiency. At this stage, he may recommend a full powerflush if the level of sediment is causing concern.

Fit for purpose – the final stage of your boiler’s service will be a series of checks to ensure it is fully working and safe to use. All settings will be put back if altered during the service and the boiler’s pressure will be checked and if necessary, re-set. Then a final visual check will be conducted to ensure all is as it should be and there are no issues or leaks.

Boiler service record – as the engineer conducts the service, they will make a record of each check plus note the boiler pressure. You will be given a copy of this information in the form of a service certificate which you should keep for your records.

The whole process of correctly servicing your boiler should take around one hour.

How Much Does it Cost to Service a Boiler?

When it comes to how much is a boiler service, the price will depend on the size of your gas boiler and the type you have. But you can expect the cost to typically be between £60 and £150. You may also need to factor in the cost of repairs and any replacement parts, should your qualified engineer find anything untoward.

It is worth checking the terms of your warranty as the cost of any repairs as a result of an annual boiler service may be covered. You can also look to take out a Boiler Service Plan, which is a pre-paid package, which in most cases you will be able to pay for monthly.

Or you may already have boiler repair cover on your home insurance policy.

How Often Should You Have Your Boiler Serviced?

A boiler service once a year is widely recommended and most boiler warranties actually specify an annual service in their terms. Should anything go wrong with your boiler and you have failed to have it serviced annually, you could invalidate the warranty or at least be asked to pay for any replacement parts yourself.

And time of year for the service is important to consider to, as the ideal is to have it completed before the winter months, so you have peace of mind as the cold weather kicks in.

However, you don’t have to wait a full year between services if feel your boiler could do with an ‘MOT’, particularly if you spot any signs that your boiler may not be working as well as it should.  And if you notice any potential symptoms of carbon monoxide poisoning, as well as seeking medical help, it is essential to get all your gas appliances, including your boiler inspected by a Gas Safe Engineer as soon as possible.

Is it a Legal Requirement to Have Your Boiler Serviced?

For domestic properties occupied by the owner it is not a legal requirement to have your boiler serviced, however, as we have already highlighted, your boiler warranty and even home insurance may require you to do so as part of their T&Cs.

However, landlords who rent out their property are required by law to have all the property’s gas appliances, including the boiler serviced annually by a Gas Safe engineer. This is to ensure the appliances, as well as emission levels are working efficiently and legally safe.

Can I Service My Boiler Myself?

You should never try to service your boiler yourself as by law, only Gas Safe registered engineers are allowed to carry out boiler checks and services. And if you do it yourself, you will invalidate the terms of your warranty as well as potentially make some dangerous mistakes.

It is also illegal for an inappropriately trained or unqualified engineer to work on your boiler, so always check their credentials. They should be carrying their Gas Safe registered ID card or, if any doubt, you can check they are legitimate by checking on the Gas Safe Register website.

What Can You Do To Protect Your Boiler In Between Boiler Services?

As well as getting your boiler serviced every 12 months, you can also take some key boiler maintenance steps which will help to protect your boiler between annual appointments and reduce the risk of any major repair work being needed.

Here’s some of the most effective things you can do to keep your boiler healthy between services:

  • Check the boiler pressure – get into the habit of regularly checking the boiler pressure reading on your boiler and top it up if need be. The ideal pressure is between 1 and 2 bars, depending on your boiler model so if it is below 1 bar, then the boiler will need repressurising.
  • Make sure you have a blue flame – your boiler will have a pilot flame for ignition and if your boiler type has it visible, then it should be a vibrant blue in colour. A flame that is orange or yellow means there could be an issue, so you need to get a qualified engineer to check it out.
  • Turn the heating on regularly – your boiler needs to be regularly used to keep it happy and running efficiently. However, during the summer months, we have a habit of turning the central heating off. To prevent the boiler losing its edge, if you like, it is a good idea to run it regularly, even if it’s for 15 minutes a couple of times a month, especially during the warmer season. This way you keep all those internal parts moving as they should and prevent a potential breakdown come winter, when you really need that warmth!
  • Keep your boiler clear – you want to avoid anything that may block your boiler’s air vents or flues, including the ones outside so check that there isn’t any unnecessary clutter around your boiler, and it is properly ventilated.
  • Bleed the radiatorsyour radiators can also affect the efficiency of your boiler and your heating system so periodically check they are working properly. If you have radiator noise, cold spots or radiators that don’t fully heat up, it could be due to trapped air, which can be released by bleeding each radiator affected.
  • Avoid a frozen condensate pipe – your boiler’s condensate pipe takes acidic waste water away from your boiler and to an outside drain. And as main part of the pipe is outside, it can freeze during cold weather, which can create a blockage that may cause your boiler to shut down. Insulating the pipe can help to prevent it freezing as can turning the boiler thermostat up during the winter. If your pipes do freeze, it is something you can quickly and easily rectify, by using hot, not boiling water poured on the pipe to thaw it out.
  • Get a carbon monoxide alarm – if you haven’t got one already, then make sure you install an audible carbon monoxide alarm in your home, ideally at least one metre away from the boiler. While not protecting your boiler, a carbon monoxide alarm is an essential early warning system that will help to protect you and your family. Just don’t forget to test it periodically to ensure the batteries are working and replace when needed.
  • Get a Powerflush particularly if you live in a hard water area, limescale can build up inside your boiler and pipework, which if left untreated can corrode and ultimately cause a full boiler breakdown. Sludge – which is limescale along with rust and general debris – can be reduced and even removed with a powerflush, which pushes high volumes of water through the system to clean it out. Boiler pressure issues as well as noisy radiators are just two signs that you may have a sludge build up and a powerflush could be due. You will need a heating engineer to carry it out.
  • Install a Magnetic Filterand finally, to prevent sludge from building up between annual boiler services, you can ask your engineer to git a magnetic filter which removes iron oxide and black sludge build-up in your system. It then provides ongoing protection against further build-up.

Is a Boiler Service Worth it?

Most definitely. It takes minutes to book a boiler service, but it can prevent or detect many boiler faults before they become a problem as well as help to ensure your boiler is healthy and working efficiently. Here’s why an annual boiler service is worth the time and effort:

Cost effective

While it may cost you around £100 to get your boiler serviced, it will pay for itself in the long run. Not only does it keep your warranty valid – and many repairs may be covered by its T&Cs – but it can prevent a small repair from becoming a large and expensive one. And it can keep your boiler running effectively for longer, saving you the expensive of buying a new boiler sooner than expected.

Energy saving

A serviced boiler is more likely to be running at its best for the rest of the year, meaning it maintains its energy efficiency. And this will have a positive knock-on effect on your home’s energy bills.


The old adage, ‘prevention is better than the cure’ is a wise one to follow, and certainly applies to your annual boiler service! Alongside proper use and maintenance, getting your boiler thoroughly checked by a professional every 12 months can keep it in good working condition as well as preventing minor issues escalating into major – and expensive – repairs.


Your home is your castle, and it is where you should feel safe. So, ensuring your gas boiler and heating system is working as it meant to should be a home maintenance priority. An annual boiler service is quick and easy to arrange, and should take no more than an hour, once a year. But that time and money is well spent as it will play a key part in ensuring your boiler doesn’t develop a fault that could prove dangerous and even potentially fatal to you and your loved ones.

And for this reason alone, there is no doubt that a boiler service is worth it.


  1. Boiler services – A complete guide for homeowners – Viessmann
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