How Often Should You Have A Boiler Service?

How Often Do You Need A Gas Boiler Service?


By the end of this short article you will understand how often a gas boiler needs to be serviced and exactly why that is. So, stick with it.


The majority of people who own a home in the UK also own a gas boiler, but how often does your boiler get serviced? Just as importantly, how often should it be serviced?

The answer to the second question is undoubtedly, annually.

And whilst you have a Gas Safe trained heating engineer on site you should also get him or her  to check out any other gas appliances that you have in the building.

So, you may ask, if a boiler appears to be working normally why would you need a boiler service?

The answer mostly revolves around the gas combustion process and what is required for that to happen safely.

For any gas fuel to burn safely it must be mixed with the correct amount of oxygen.  The required mixture of gas and oxygen alters for each gas type; methane, propane and butane, but for methane (natural gas that is piped to our homes) we need one part gas to two parts oxygen.

Make a mental note of that – you need plenty of oxygen.

This mixture is critical to understanding what the dangers are; even if your boiler, gas fire, Ascot or cooker appears to be working normally.

With normal, correctly managed combustion, the products of combustion should be carbon dioxide (CO2)and water vapour (H2O). Those are the harmless gasses that should travel away from the flames in your cooker or up the flue of your boiler.

If something happens to prevent the delivery of sufficient gas or oxygen to your gas burning system; such as a build-up of dust, dirt, or soot then incomplete combustion may be the result, and this means that the products of combustion may include the potentially lethal carbon monoxide.

Carbon monoxide (CO) as well as being highly toxic when breathed in by human beings is also potentially highly explosive when combined with gas fuel.

And that in a nutshell is why you need to have gas appliances checked annually – because dirt and dust builds up and the consequences may not be good.

Note: Modern boilers are generally designed to be room sealed. Meaning that the air that comes into them comes from outside and the products of combustion are expelled to the outside as well. So these offer less potential for danger than older style boilers, but they still need to be checked in the same way.

Other hazards, of course, include the rare occurrence of gas leaks. These are checked for when the visiting heating engineer checks the gas pressure. Gas pressure checks (so called tightness tests) are a mandatory element of a gas boiler service.

What does a Heating Engineer Do During a Boiler Service?

Well, he obviously inspects the inner workings of the boiler and repairs and replaces as necessary, but in addition to that he will also analyse the exhaust gas from the boiler, check that the gas pressure is correct (since that will affect the gas/oxygen mixture and ensures that there are no gas leaks) and he will check the airways to your appliance.

That last point is also pretty crucial. Gas regulations in the UK explicitly and very precisely define how much ventilation should be available for the various gas appliance types. This is not just so that you have plenty of good air to breath; it is to ensure that the gas/oxygen mixture is adequate for proper combustion. It is also required to make open-flued chimney systems work properly.

Yet any heating engineer will tell you that it is very, very common to find that people have deliberately blocked strategically positioned air vents between adjoining rooms and vents going to the outside of their dwellings.

It’s easy to understand why people do this (to stay warm), but we hope that we have now explained why these vents are there in the first place and why it is very unwise to block them off?

Boiler And Other Appliance Problems – What To Look Out For

Here is a picture of a gas boiler that SafeSure Plumbing and Heating Ltd. were called out to examine in May 2015. The home owner was concerned that it hadn’t been working very well.

picture of a badly corroded gas boiler

There had evidently been a slow water leak for a very long time, which had caused so much corrosive damage that we had to declare the boiler immediately dangerous and cap-off the supply to that appliance until the boiler could be replaced.

This was an extreme and fairly unusual case, but it serves to illustrate what can be happening – unknown to you –  behind the covers of your gas boiler, or other gas appliance. It demonstrates why routine inspections are important.

Other signs to look out for are:

  • Any soot and signs of burning. This could be around burners on any appliance, or around the casing of a boiler.
  • Increased condensation in the room.
  • Explosive ignition within the boiler (starting with a bang).
  • Unusual looking flames. Natural gas flames should burn blue and upright; not big, orange and wavy.
  • Flames should be close to the burner, not too far lifted off.
  • Blocked or sealed airways.
  • Any other irregularities in the appearance of you gas appliance.

If in doubt call a professional.

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If your boiler is due a service or if you have any concerns and you happen to be in Bedfordshire, Hertfordshire or Buckinghamshire, please call us on 07850 462932.

Cost of a boiler Service

Typically in the UK most domestic boilers are serviced at a cost to the consumer of between £55 – £95, depending on where you are in the country. Call us for a price quotation.

Check out our article on the pros and cons of combi boilers, here.