When to replace a boiler – signs it's time to buy a new one

Is your central heating system working too hard to warm your home?

The boiler is the engine of your home. Its primary job is to keep all your household facilities working and running smoothly. Sometimes things can go wrong – whether old or new – so it's important to know the signs so you can spot when you need to replace a boiler.

You boiler is a vital appliance that sends hot water to your radiators and underfloor heating. Plus, of course, it's the essential source that supplies endless hot water to taps in your kitchen, bathroom and utility room for all your daily needs.

When to replace a boiler – signs it's time to buy a new one

kitchen with dining table

(Image credit: Worcester Bosch)

Only engineers registered on the Gas Safe Register are legally qualified to install, repair or move a central heating boiler (opens in new tab). Carbon monoxide poisoning can be fatal so always check the tradesperson's Gas Safe Register ID card to ensure they have the right qualifications for the job.

Here are the most common reasons it could be time to invest in a new central heating boiler for your home:

1. It’s an old boiler

If you have an older boiler that hasn’t been updated for a number of years, it’s likely that you will need a replacement. 'Experts recommend that you get a new boiler when it is around 15 years old,' explains Andy Kerr, Founder of smart home systems installer BOXT.co.uk. (opens in new tab)

2. It's wasting money

'In those 15 years technology will have drastically advanced – especially in the world of boilers,' continues Andy. 'What was once a white, industrial-looking box stuck on the wall can now look like something out of an Apple store. Not only visually but mechanically they've improved. Quieter, compact, and more efficient than ever – modern boilers save you money.'

3. It's no longer energy efficient

The thing that impacts your boiler efficiency the most is its age. When an old boiler uses more energy than necessary to heat your home and water, it is producing more carbon emissions. When fossil fuels such as gas and oil are burnt with oxygen, they produce CO2, which is a greenhouse gas that contributes to climate change.

There’s been a lot of talk about a gas boiler ban in recent months, as the government ramps up its net zero plans for 2050. 'Boiler efficiency is measured by how efficiently your boiler turns its fuel into heat energy,' says Mark Glasgow, Director of The Edinburgh Boiler Company (opens in new tab) 'Essentially, an efficient boiler uses the least amount of energy and money and produces fewer carbon emissions. It’s a win-win situation for both you and the planet.'

4. It’s broken or faulty

Even a boiler still under the recommended age and warranty can get a fault. It's important to have an annual service (preferably in the warmer months) to pick up any problems.

Faulty boiler signs to look out for

vaillant

(Image credit: vaillant)

There are a number of ways a boiler can become faulty. Each problem has warning signs you should look out for. If your boiler constantly continues to suffer from any of the below issues, it may be more cost-effective to recognise when to replace a boiler, rather than repairing an old one.

Leaks or drips

Your boiler can begin to leak in a number of places. To really pinpoint the exact problem, you need to know where your boiler is leaking from. The most common cause of a leaking boiler is a broken component inside the boiler. The pump seal or pressure valve could be damaged.

If the pressure valve is the culprit, your boiler pressure may be too high (see below). If it is the pump, then it may simply have become worn out from excessive or constant use over time.  Other common places you may find leaks include the pipes of your system. This can be due to corrosion, so it’s best to get in touch with an engineer who will be able to correctly identify the problem.

Lower pressure

Low boiler pressure can be caused by a number of factors, including water leaks, bleeding radiators (opens in new tab) as well as the need for a new pressure valve.

'It’s easy to check the pressure of your boiler. All you need to do is look at the built-in pressure gauge. If the needle is below 1, you may have a problem that needs addressing,' says Andy Kerr.

If you’re losing pressure quickly – even when re-pressurising your system – get in touch with an engineer to find out the underlying problem.

Higher pressure

If a pressure gauge measures above 2.5 it's considered too high. Too much water in the system or malfunctioning boiler parts are usually the main culprits. The extra pressure will put stress on the system which can lead to cracks and leaks.

kitchen

(Image credit: Vaillant)

Excessive noises

Strange noises coming from your radiators or system is usually an indicator there is a fault. Sometimes, the sound itself can pinpoint the problem:

 Gurgling Are you hearing bubbling noises? This is usually caused by air trapped in the radiators, which can be rectified by bleeding radiators. Or, there is trapped air in the main system.

Kettling This is a term used when a whistling is heard similar to that of boiling a stovetop kettle. This may be the result of limescale build upon key internal components which then overheat.

'Not only is this a noise issue,' says Ben Mars, resident Gas Safe Engineer at Heatable.co.uk (opens in new tab), 'but consistent overheating can also result in the development of cracks and broken seals in the heat exchanger or nearby components, resulting in a leak.'

Humming If there is a humming or vibrating in the system, this could signify that the heating elements are not working properly. This suggests there’s a fault. 'All boilers have some level of noise as part of its normal operation,' says Ben. 'If it's a new noise, then it's more likely there is a problem. Common causes are loose components, high water pressure or the pump running too fast.'

Dripping The likelihood is there is a leak somewhere which can lead to pressure loss or electrical component damage.

Clicking or tapping This generally means there may be an ignition failure.

No hot water

If a boiler is heating the house but not supplying hot water, the diverter valve may be defective. This problem is common in older boilers that have had a lot of use. The diverter value becomes worn, weakened or seized.

No heating

Faulty thermostats that control the temperature of the room may be the culprit. Or, boiler pressure may be to blame.

If neither are guilty it's time to call an engineer. 'Common reasons for this particular fault are broken diaphragms and airlocks, a motorised value failing,' says a spokesperson at Auragas (opens in new tab). 'These issues will need a professional heating engineer to come and fix or replace the faulty part.'

heatable

(Image credit: Heatable.co.uk)

Constant 'lockouts'

A boiler lockout is a shutdown procedure that initiates when the boiler is not working. If this is happening regularly and engineer callouts are becoming more frequent it may be time to consider whether a new boiler would save money in the long run. The older a boiler gets, the more difficult may be to source new components or parts. So, in fact, it will have become Beyond Economical Repair (BER).

If you notice any of these signs, seek the help of a professional right away. Visit the Gas Safe Register (opens in new tab) to find a qualified engineer near you.

Get a free quote for a new boiler

Ideal Home has partnered with boilerguide.co.uk to provide a free quote for your new boiler.

Rachel Homer has been in the interiors publishing industry for over 15 years. Starting as a Style Assistant on Inspirations Magazine, she has since worked for some of the UK’s leading interiors magazines and websites. After starting a family, she moved from being a content editor at Idealhome.co.uk to be a digital freelancer and hasn’t looked back.