This is what I did when my radiators stopped working when it was sub-zero outside — and I didn’t need to call a pro
This is what to check first if you have the same problem
Why oh why is it that radiators and boilers always seem to decide to play up just when we need them most? Its like they wait all year for temperatures to drop just a little bit to play up.
Last week, sitting working from home, I became aware that could no longer feel my toes. Upon realising this, I went to see whether the heating was on, which it was – and yet, the radiator nearest where I was working was freezing cold. Typical.
1. Checked where the radiator was cold
The first time you put your heating on is always a little bit stressful – will it work or won't it? When I checked the radiator in the kitchen a little more thoroughly I found that it wasn't actually cold all over – just at the top. At the bottom it was warm, although not overly so.
According to Michael Zohouri, founder of Pyramid Eco, there are several reasons why a radiator might not be heating up evenly.
'The first thing to look at is where the radiator is cold,' picks up Michael. 'If it’s cold at the top but warm at the bottom, that usually means trapped air. If it’s cold at the bottom but warm at the top, that often points to sludge in the system restricting the flow of hot water.'
Michael Zohouri is the founder of Pyramid Eco, bringing over a decade of experience to the company. His expertise spans energy-efficient retrofitting projects, including insulation, solar, and heat pump installations. Committed to addressing challenges like thermal bridging and improving air quality, Michael focuses on creating healthier, more sustainable living environments while reducing energy costs for residents.
2. Checked the boiler pressure gauge
The next possible culprit of my radiators not heating up properly was, according to Michael Zohouri, my boiler pressure.
'Check the boiler pressure gauge – in most homes it should sit between 1 and 1.5 bar when the system is cold,' explains Michael. 'If it’s too low, the radiators will struggle to heat up properly. If multiple radiators are cold at once, the issue is more likely with the boiler, pump or thermostat rather than the radiators themselves.'
'If pressure is low, there is usually a filling loop under your boiler,' says Gordon Chalk, managing director at Next Level Underfloor Heating and Screed Solutions LTD. 'This is a bendable hose with two buttons. Look at the manual for your boiler to get the exact steps, but in general, you slowly open both valves, keep an eye on the pressure gauge as it rises, and then close them tightly when the right pressure is reached. This hack is very important because low pressure may keep the boiler from moving water properly or even starting up at all as a safety measure.'
Along with Alan Houghton, Gordon is managing director at Next Level Underfloor Heating and Screed Solutions LTD where he helps property owners get warmer and more comfortable with underfloor heating and proper floor screed.
3. Bled the radiators
Ideally, radiators should be bled once a year, before heating season arrives.
'Bleeding radiators is a simple option,' says Gordon Chalk. 'Just get a radiator key and a cloth to catch the drips. Make sure your basic heating system is not on then find the flow valve at the end of the radiator – most of the time at the top.
'Put the radiator key in and slowly turn it to the left,' continues Gordon. 'You should hear a hissing sound as the air leaves. When the water starts to drip, close the valve by turning the key to the right (use your cloth!). This hack makes sure that the hot water can fill the whole radiator and that it gives off the most possible heat. It works by pushing air out of the way.'
Shop kit to bleed a radiator
Sturdy and easy to turn, keep a set of these handy all over winter for when you need to bleed your radiators.
Perfect for all kinds of tasks but, thanks to their high absorbency, also ideal for mopping up dirty radiator water.
This handy little kit comes with everything you need to bleed your radiators without getting water everywhere.
4. Checked the radiator valves
Despite the home upgrades we have made to keep our house warm, the radiator in our already cold hallway wasn't heating up at all when I checked – and it turns out the problem lay with the valves.
'If a radiator is not warm at all, the thermostatic radiator valve (TRV) should be checked first,' explains Gordon Chalk. 'If it's off or set to zero, the problem might be fixed by just turning it up.
'However, the pin inside the TRV can get stuck sometimes, especially after not being used for a while (like over the summer),' continues Gordon. 'Take off the plastic TRV head to check. There should be a little metal pin visible. If it's stuck, gently tap it with a hammer, or use pliers to pull it up – but don't bend it. The radiator should start to heat up if the pin comes loose and you put the head back on. This hack lets hot water flow into the heater by making sure the valve is open.'
5. Considered a professional power flush
Thankfully, after bleeding the kitchen radiator and sorting the stuck TRV on the hallway radiator, my problem was resolved. However, I did also consider a powerflush to ensure I was making the most of my central heating system.
'Another cause of cold radiators that people don't always think about is sludge growth in the system,' says Gordon Chalk. 'Radiators can develop cold spots – or even be completely blocked because of rust and dirt that build up at the bottom over time. If a radiator is cold at the bottom and warm at the top, even after bleeding it, there is probably sludge in it.
'A professional powerflush is the best way to fix the problem, but amateurs can try to get the fluid moving by turning off the heat, separating the problematic radiator, and carefully draining it (it will be dirty, so drain it into a bag!). Then fill it up again. This is a more complicated and messier hack, but it can help with some of the things that are blocking it for a short time.'
FAQs
How can you keep radiators running properly?
In an ideal world, you wouldn't need to wait until something went wrong to take a closer look at your radiators.
'In the UK, a Gas Safe registered engineer should service your boiler once a year,' points out Gordon Chalk. 'This makes sure it's safe and efficient, finding problems before they cause breakdowns.
'Also make sure pipes are insulated,' adds Gordon. 'Water loses heat if it travels through pipework that isn't insulated. Think about covering up pipework that isn't in a warm space, like in basements or lofts.'
'Regular maintenance is key,' picks up Michael Zohouri. 'Bleeding radiators at the start of the heating season to remove trapped air before cold spots develop and keeping boiler pressure within the correct range so hot water circulates properly around the system.
'You also want to make sure furniture and curtains aren’t covering radiators and stopping them from circulating heat around the room,' adds Michael. 'A radiator that cannot release heat efficiently will force the system to work harder and waste energy.'
What radiator issues should be left to the pros?
While many radiator maintenance jobs can be carried out on a DIY basis, there are some dangerous DIY jobs that are best left to the professionals.
An annual service is the most obvious, but there are other, more complex reasons for radiators not heating up that should be left to the pros too.
'An unstable heating system is a common cause of patchy heating, particularly when some heaters are hot and others stay cool or take a long time to warm up,' explains Gordon Chalk. 'This isn't about air – it's about how water flows. If the radiators near the boiler get all the hot water first, those further away will have a hard time working. Homeowners can try a basic change, but a full system balance is usually best done by a pro.'
What’s the life expectancy of a radiator?
According to The Radiator Centre, the average radiator will last between 10-15 years.
Over time, even designer radiators can corrode internally, leading to sludge build up and rust – be on the lookout for rust patches appearing externally too.
'Sludge is made up of rust, dirt and debris that settles in the bottom of radiators and blocks the flow of hot water,' explains Michael Zohouri.
Checking your radiators are running properly is just one step you can take to prepare your home for cold weather – there are lots of external jobs to get done and dusted too.
