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Site last updated 27th January 2019
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What is a boiler service, exactly?
Many people are a bit puzzled by boiler servicing. Puzzled about what it is, why it should be done, and what happens if it is not carried out regularly. There is a suspicion that very little is done really during a boiler service and it's a work creation scheme dreamed up by lazy gas engineers. This isn't true (mostly!), so here are some proper answers...
What it is...
It's checking, cleaning, testing and pre-emptive fault-spotting, really, with the emphasis on testing all the different functions of an appliance for correct and safe operation.
Unfortunately, different companies have widely differing ideas about what should be done to service a boiler. At one extreme some (bigger) companies have their engineers do no more than put a probe in the flue outlet to analyse the contents of the flue gasses, and if all is well, announce the boiler is working correctly and start writing out the invoice. Beware these companies. Their short-cutting can often be spotted by looking carefully at the wording of their offering. When you ask for a "boiler service" you will be offered an "annual safety check" instead, misleading you into thinking you are getting a full annual service.
At the other extreme there are gas installers who check the gas pipework, ventilation, clearances etc then take everything to pieces, clean and reassemble, and spend ages testing the operation of every single aspect of the boiler functions for safe and correct operation. It's no wonder that boiler service prices vary widely is it? (I fall firmly in the second camp, by the way.) The first method is an outrageous short-cut and does nothing to confirm the boiler is actually safe to use.
Why it should be done...
When a boiler or gas appliance appears to be working well, there 'could' be hidden faults. These will be revealed by a proper service. A good example would be the device which turns the gas off if the pilot light blows out. If this fails to work when needed you could have gas leaking into your house, but how do you know if yours still works? This will be tested during the service procedure. Here is the full service procedure if you want to know in complete detail what a proper service comprises.
What happens if not carried out regularly...
Well, in most cases, everything will be fine, but you won't know for sure. The whole gas installation is examined and tested for correct installation and operation. A wide variety of things go wrong with gas installations and the gas regulations exist to make sure installations are safe. Proper servicing, in summary, makes sure your installation is safe.
How often should servicing be done?
It's very much up to you. How often do you want your system to be inspected and confirmed safe? Most manufacturers recommend annually. This is much more important once a boiler is a few years old than when it is brand new in my opinion, and more important if the boiler has an open flue (vertical, chimney-style) rather than a balanced flue (horizontally, through the wall).
My view is that open flued appliances should be done every year. This is because it's mostly open flued appliances that cause carbon monoxide deaths. It is so easy for combustion products to get into the house when something goes wrong with the flue (or the ventilation), and frequent servicing helps identify flueing problems early.
Balanced flue appliances are less critical. Manufacturers still say once a year but many gas fitters privately think bi-annually is adequate, mainly because flue problems are rarer and usually less serious. And also because they draw clean fresh air from outside. This means the burner airways don't get accumulations of carpet fibres, pet hairs etc (called 'lint' in the trade) in them, and cleaning needs to be done less often.