While we're seeing some milder temperatures than we may be used to in December, it's an ideal time to check that your radiators are in good working order ahead of the inevitable cold snap (and not to mention the festive period).
If, like me, you've always felt pretty confident when it comes to how to bleed a radiator, it might surprise you to know that you should be bleeding your radiators in a very particular order, and for good reason.
What order should you bleed radiators in?
It turns out that the order in which you bleed your radiators matters, and the consensus among the experts I spoke to for this article agreed that you should start with the radiator furthest away from the boiler.
'Bleeding in the wrong order can actually shuffle air around the system rather than removing it,' says Patrick Garner, Gas Safe Engineer at Heatable. 'By starting at the furthest radiator, you’re letting the system release air in a logical, consistent direction.
'It prevents pockets of air from getting pushed into radiators you’ve already sorted, and it helps your heating run more smoothly - with fewer cold spots and less strain on the boiler.'
Patrick is a seasoned Gas Safe certified engineer and the dedicated leader of the heating system installations team at Heatable, with extensive experience in boilers, heat pumps, and home energy solutions.
'Start bleeding at the radiator furthest from the boiler on the lowest floor, work radiator by radiator towards the boiler, then move upstairs and repeat from the furthest to the nearest,' says Nicholas Auckland, MD at Trade Radiators. 'If you're in a bungalow, start at the furthest radiator and work back to the boiler.'
Logic might tell you to start with the radiators upstairs first, but as Sam Carter, radiator expert at Appliances Direct says, this may not be the most effective method. 'If you bleed the upstairs radiators first, trapped air bubbles may eventually rise up and get stuck in the radiators you just cleared.'
But by starting with the radiators furthest from the boiler on the ground floor, before repeating the process upstairs, you will achieve a better result, as Nicholas explains: 'Air rises and collects in high points and at the ends of long runs, so tackling the hardest to purge first prevents pockets of air being pushed further out into the system. By the time you reach the upstairs rads, most air has migrated there and is easy to release, which reduces repeats and helps the pump circulate water evenly.'
Nicholas Auckland is a heating and energy expert with almost 20 years of experience in the industry, as well as the Managing Director of Trade Radiators.
Sam is a radiator and heating expert with Appliances Direct. He is dedicated to helping customers as they shop for radiators, heaters, dehumidifiers, and air conditioning online.
Should you bleed all your radiators or just the ones that feel cold at the top?
It's a good idea to bleed all of your radiators, as any trapped air can move around the system, affecting radiators that were previously working without issue.
'In reality, if one radiator needs bleeding, there’s a good chance several do. A quick check of the whole house only takes a minute,' says Patrick.
By following a specific order when it comes to bleeding, 'It also means you're less likely to miss a radiator, adds Lincoln Smith from Custom Heat. 'That said, if you've got a radiator that's clearly cold at the top and hot at the bottom, that's a dead giveaway it needs bleeding regardless of where it sits in your sequence.'
Lincoln Smith, Managing Director of Custom Heat, a heating company based in the Midlands and South West.
How often should you bleed your radiators?
Using a radiator bleeding tool, like this one tested by Ideal Home team member Lauren, can make even speedier work of bleeding your radiators
Now you know the correct order in which to bleed your radiators, how often do you need to do it? Bleeding your radiators is one of those things you should do every year, before the cold weather hits. But if you are finding your radiators are cold at the top, when the heating is on, on a regular basis then that's a sign that something is amiss.
'If you're having to bleed the same radiator every few weeks, that's not normal,' explains Lincoln. 'It means your system is drawing air in from somewhere, possibly through a leak or a faulty valve, and that needs investigating by a professional.'
How do you know if you've bled your radiators correctly?
If you don't already have one, it's best to use a radiator bleeding key, like this one from Amazon (£4.99), a cloth and something to use as a tray to catch any water drips when bleeding your radiators. Alternatively, you could try an all in one option, like this WENKO radiator bleeding tool, £10.15 also from Amazon.
If you don't have one, it is possible to bleed a radiator without a key, although this should be an emergency measure rather than a go-to measure.
Once you've used the right kit, and are approaching your bleeding in the right order, there are key signs to watch out for to ensure you've done it properly. 'You’ll know a radiator is properly bled when the initial hissing of air stops and you get a steady, bubble-free stream of water from the bleed point,' says Nicholas. 'Close the valve as soon as the water runs cleanly, then wipe the valve area dry and nip it shut without over-tightening. When you turn the heating back on, that radiator should heat evenly top to bottom with no cool top edge.'
FAQs
What should you do if too much water comes out while bleeding your radiators?
When bleeding your radiators, you can expect a little bit of water to come out, but losing too much water can cause another set of issues you'll need to resolve.
'You only want to see a tiny trickle of water, literally a few drops, before you close the valve,' says Lincoln. 'If you're getting a steady stream of water pouring out, you've opened the valve too far or left it open too long.'
So what's the issue if too much water comes out? 'The real problem with losing too much water is that it drops the pressure in your system,' Lincoln explains. 'Most modern boilers have a pressure gauge, usually on the front, and it should read between 1 and 1.5 bar when the system is cold. If bleeding your radiators has dropped the pressure below 1 bar, you'll need to repressurise your system using the filling loop, which is usually a braided hose underneath the boiler. If you're not confident doing that, call a heating engineer.'
What happens if you bleed a radiator while the heating is on?
When you consider that the water flowing through your radiators when the heating is on can be between 60 and 80°C, it can be an incredibly dangerous time to bleed your radiators. 'Bleeding radiators with the heating on is a recipe for scalding yourself with hot water or steam,' says Patrick.
The system is under higher pressure when hot, so that the water can escape much more forcefully. Always turn the heating off and let the radiators cool completely - it’s safer and makes the bleeding process more effective.'
Will bleeding fix a radiator that is cold at the bottom?
No, bleeding won't help a radiator that is cold at the bottom. Bleeding releases air from your radiators, and as trapped air rises to the top of the radiator that's where you'll notice it's considerable cooler when the heating is on.
However, if you are noticing that your radiators are warm at the top and cold at the bottom, that's more likely a symptom of sludge build up rather than trapped air. To resolve that, you can try flushing the radiator, or you can give your whole heating system a power flush to clear it out and get it in efficient working order again.
While you're bleeding your radiators, if you notice signs of a radiator leak you can try these DIY tips to try and fix it before calling in the pros.
