The 5 signs your boiler is about to stop working and how to fix the issue before it packs up this winter
Warning signs that mean you should take action now
Why is it that boilers, radiators and central heating systems in general always seem to choose the coldest months to stop working properly – just when we come to rely on them the most?
Rather than wait for something to go wrong or finding out you're going to have to replace your boiler, it turns out there are lots of symptoms that could point to a problem waiting to happen – and once you know what to be on the lookout for, you can fix the issue before it ever causes you any stress.
1. Strange noises
If you want to keep your house warm this winter, you need to know how your boiler is running – so spend a little time listening to it.
'One of the earliest signs of a problem is unusual noise,' elaborates Michael Zohouri, founder of Pyramid Eco. 'Boilers should run with a steady hum. If you hear any banging, whistling or gurgling sounds it’s usually a warning sign. There could be trapped air, low pressure or scale and sludge building up inside the system.'
'If your boiler has started to make odd sounds, there could be a number of causes, including a faulty pump, air in the system, sludge or rust, low water pressure, or even an accumulation of limescale,' picks up Stephen Day, operations manager at iHeat. 'One particularly common issue is 'kettling,' where the boiler sounds more like a whistling kettle than a heating system, caused by a build-up of limescale or sludge around the heat exchanger that restricts water flow and causes trapped water to overheat and boil.
'Kettling is most common in hard water areas, where limescale naturally builds up more quickly, as well as in older or neglected boilers that haven't been serviced regularly,' adds Stephen. 'In severe cases, it can cause your boiler to stop supplying hot water or even shut down entirely, leaving you without heating when you need it most.
'For kettling specifically, the problem is treatable by having a professional heating engineer carry out a power flush or chemical cleanse to remove sludge and limescale,' adds Stephen. 'You can also install a magnetic filter to prevent future debris from circulating, and use a scale reducer in hard water areas where mineral deposits accumulate more quickly.'
Easy to fit and more compact than most, this magnetic boiler filter also has little windows to allow you to see all the sludge and debris it is collecting.
Michael Zohouri is the founder of Pyramid Eco, a company dedicated to renewable energy and energy efficiency. He has extensive experience designing and installing heat pumps, improving ventilation, and upgrading insulation to make homes more efficient, comfortable, and sustainable.
Stephen Day is the operations manager at iHeat, with over a decade of experience as a qualified heating engineer and home cooling expert. He specialises in efficient, modern solutions for heating and air conditioning across the UK.
2. Drips and leaks
It really does pay to give your boiler a thorough onceover every so often – that way you will notice any issues as they crop up, leaks included.
'Leaks are another common indicator of a problem,' explains Stephen Day. 'They're often caused by corrosion in the pipes, but could also be down to a worn-out or broken component, such as a cracked heat exchanger.
'If you do find a leak, you should inspect it carefully, as it can sometimes be something as simple as a loose connection that needs tightening, meaning you don’t need to bring in a professional right away. If the leak continues after checking for loose connections, it's best to call in an engineer who can find and then source the replacement parts needed.'
3. Heating not working efficiently
Noticed your radiators aren't heating up properly or that your water isn't hot when it should be? Problems with your central heating are tell-tale signs that your boiler could be on the brink of a breakdown.
'Poor heating performance is a red flag to watch for, as if your boiler isn't heating your home as well as it once did, this could be down to an issue with the heat exchanger or the burner – two of the most common components that fail in a boiler,' warns Stephen Day. 'Beyond being irritating, restricted flow means your boiler has to work harder and burn more gas to achieve the same result, pushing up energy bills and placing extra strain on internal components.'
'Inconsistent hot water is another sign,' adds Michael Zohouri. 'If the water runs hot and cold during use, it often points to a failing sensor, diverter valve problems or general internal wear. Many boilers fail completely not long after this starts if it is ignored.'
4. Low boiler pressure
Your boiler pressure should be something you are regularly checking if you want to keep abreast of any potential problems.
'Another sign is pressure that keeps dropping,' explains Michael Zohouri. 'If you are regularly having to top the pressure up, there is almost always a leak somewhere in the system or an internal component starting to fail. A healthy system should hold pressure steadily.'
The ideal pressure for your boiler is 1 to 1.5 bar. You can top it up yourself using the filler valve, which looks like a little hose. Depending on the type of boiler you have, you will need to open the value a little until the pressure goes up and then close it off again.
5. Pilot light issues
If your boiler has a pilot light, this can be a great indicator of problems.
'A yellow or lazy pilot flame instead of a strong blue flame is a sign that should never be ignored,' advises Michael Zohouri. 'It can indicate poor combustion or ventilation issues and needs checking straight away.'
'If a boiler’s pilot light isn't staying lit, it can indicate a variety of possible issues,' picks up Stephen Day. 'For instance, there could be a build-up of deposits in the pilot light compartment or even a fault with the 'thermocouple' – the sensor that measures temperature.
'For a pilot light that's gone out, you should be able to address this problem quickly and easily just by restarting your boiler, though if you're not sure, you can always call a Gas Safe Engineer for further assistance,' adds Stephen.
What should you do if you spot any of these signs?
Now you know what to lookout for, what should you do if you have spotted any of these signs?
'If you notice anything affecting the flame colour, smell gas, or feel dizzy or unwell when the boiler is running, turn it off immediately and seek professional help straight away,' begins Michael Zohouri. 'For non-urgent issues like pressure loss, noise or inconsistent hot water, book a qualified engineer to inspect the system.'
FAQs
How can you keep your boiler running efficiently?
In an ideal world you want to be maintaining your boiler so well that you don't run into any issues – it could also help you save energy and money.
'Bleeding radiators at the start of the heating season removes trapped air and helps the boiler distribute heat evenly,' further advises Michael Zohouri. 'Adding inhibitor fluid to the system reduces corrosion and sludge build-up, which are two of the biggest causes of boiler damage over time.'
'One of the simplest, yet most effective, ways to improve boiler efficiency is to lower the boiler flow temperature,' adds Stephen. 'Many boilers are set by default to a high flow temperature of 70-80°C, and while this ensures fast heating, it wastes energy as excess heat escapes through the boiler flue. By lowering the flow temperature to 60°C, boilers can operate in 'condensing mode,' a more efficient state that recovers heat that would otherwise be lost. This could reduce your bills by as much as 9%, meaning the average household could save around £163 a year.
'Finally, while it might sound counterintuitive, occasionally turning your heating on during warmer months for short periods (around 30 minutes) is a good preventative measure,' continues Stephen. 'This can prevent components inside your boiler from seizing up from lack of use, ensuring functionality when winter arrives.'
This is so easy to add to your central heating system yet works to effectively prevent corrosion and limescale build-up to prevent build up of anything that might compromise your comfort.
How often should a boiler be serviced?
Regular boiler servicing is one of the very best ways to keep it in tip-top condition.
'Every year, your boiler should be serviced by a Gas Safe engineer to ensure that it is running safely and efficiently,' advises Stephen Day. 'By scheduling this check before the coldest weather arrives, any potential issues can be found and dealt with well before the boiler is needed the most. Identifying faults early also allows engineers to make repairs before they become major problems, optimising your boiler's efficiency and saving you money on energy bills over the long term.
'Do not wait for a full breakdown. Most of the serious boiler failures we attend in winter start as small issues that were left for weeks or months' adds Stephen. 'Getting the boiler checked early and paying for a boiler service is usually far cheaper than repairing major internal damage later.'
Good home maintenance is key to keeping your home up and running efficiently throughout the year – and its still not too late to prepare your home for winter.
