Gas boiler servicing or repearing concept. Toolbox with tools

A problematic boiler can be troublesome at the very least and create family chaos at worst. There’s a range of issues which can affect one and whilst it’s always wise to reach out to a professional if you aren’t sure what to do or if it includes work such as electrics, there can be occasions where a little DIY knowledge will solve the problem.
Boiler issues DIY guide

  • Boiler pressure too low

On the front of the boiler you’ll find a water pressure indicator display dial. If the reading is less than 1, you have low pressure. Turn off your boiler and locate the filling loop underneath it. Open the boiler valve and listen – you will hear the system filling with water. At the same time, watch the dial and when it reaches 1.5, close the valve and turn the boiler back on.

  • Bleed radiators

Cold radiators may mean trapped air in the system rather than a boiler problem. Use a radiator key on the valve and very slowly turn anti-clockwise. There’ll be a hissing noise which is the air leaving the system – as soon as this stops, tighten the valve with the key.

  • System reset or pilot light relight

Have a look in the boiler manual for where the reset button is located and press as guided – often for 10 seconds. Boilers before 2004 usually have a pilot light so if it’s gone out, follow your user manual instructions to try to relight it.


Problems where you need to call a qualified engineer

If the quick fixes don’t work, you’re not confident enough to do the job yourself or it’s another issue, speak to a qualified boiler engineer. It’s certainly time to speak to a professional if you are experiencing any of these nasty niggles.

  • Boiler leaks or is dripping

There’s a number of reasons this can happen; pressure issues, damage to the water seals or maybe cracks due to age and use. If this is happening, only a qualified engineer can help and you should call for assistance.

  • Pilot light repeatedly goes out

If a pilot light doesn’t stay lit after following the instructions in the manual, it could be because there’s dirt in the line, a damaged thermocouple or an ignition part which needs replacing. These are all jobs for a qualified professional as they will need to run tests and inspect the parts inside.

  • No heating or hot water

Perhaps one of the first reasons you’ll know there’s a problem; a cold bath and the radiators refuse to warm even if you’ve bled them. A complete loss of both heating and hot water could be due to a variety of issues such as a broken airlock or perhaps a valve which has failed. Whilst perhaps it may turn out to be something simple, only an engineer should do the work.

  • Knocking or banging

A noisy boiler can sound scary but with the help of an engineer it can quickly be sorted. You’ll probably think that the boiler sounds like a kettle boiling and the term used is ‘kettling’. The issues include air in the system, sludge and limescale which has formed over time and a knocking sound could indicate a failing pump.
Even if you have your boiler serviced regularly, a break down can happen at any time. With winter approaching, nobody wants to feel the chill so keep your user manual somewhere handy and know who to contact if trouble strikes.


Servicing your boiler at least once a year is much more than just a basic safety check. It also helps you ensure that it’s operating effectively, as well as making sure any seals and gaskets aren’t showing any early signs of wear and tear.


Can’t I just check the boiler myself?

Whilst it’s always advisable to keep an eye on your boiler throughout the year (and not just during the winter months, when most families tend to start relying on it more); it’s important to have your boiler checked and serviced by an approved Gas Safe registered engineer.

The Gas Safe Register contains a list of approved businesses that are legally authorised to carry out gas work. You can quickly check for your nearest engineer by following his link:

To ensure your boiler is fully covered, you also need to check the terms of your warranty since failure to have your boiler serviced every 12 months could lead to it being invalid. This can be extremely costly should anything go wrong. Remember, a faulty boiler will not only waste money on energy but could also start leaking poisonous carbon monoxide. Unfortunately, because gas is both colourless and scentless this can often be difficult, if not impossible, to detect.


What can I expect from a boiler service?

If you have any specific concerns about your boiler, or the way it’s performing, then always be sure to discuss these with your chosen engineer. Other than that, the service should include a check of the heat exchanger; together with other parts of the boiler such as the flue – just to make sure that everything’s operating as it should and above all, safely.

During the service, your engineer is likely to check the different components, clean, test and undertake pre-emptive faul spotting.


Are there different types of boilers and does this make any difference to the service?


Yes: boilers can either have an open flue (which is a vertical, chimney-style version) or a balanced flue (which are horizontal and will run through your wall).

Because most open-flued appliances can easily allow combustion products to enter your home when something goes wrong with the flue (or even the ventilation); they sadly tend to cause more deaths resulting from carbon monoxide. For this reason it’s advisable to get the boiler serviced every 12 months since problems such as these aren’t usually noticeable to the naked eye.
Balanced flues, on the other hand, tend to be much less critical since flue problems are not only much rarer but usually less serious. What’s more, because they draw clean fresh air from the outside the burner airways don’t attract lint accumulations of the usual household elements such as carpet fibres, pet hairs and so on. This also means that cleaning needs to be done less often that open-flued alternatives.


What do I need to look for in an engineer?

Other than being Gas Safe registered, always be sure you understand exactly what your engineer is going to do. Unfortunately, whilst some companies offer an “annual safety check” this doesn’t necessarily mean that your boiler will be serviced; so always be sure to ask what the service does (and doesn’t) include.