How to bleed your radiators
By: Shell Energy
04 Jan 2023
Have your radiators stopped warming up fully? It may be time to bleed them. Follow these simple steps to bleed your radiators for a cosier, more energy-efficient home.
Over time, air sneaks into your central heating system and gets trapped in your radiators. While this won’t cause any damage, it will make your boiler work harder to heat your home - using more energy than necessary and costing you money.
Don’t worry about needing to call a plumber, though. It’s quick and easy to bleed them yourself.
Why do you need to bleed radiators?
Every radiator accumulates trapped air, it’s a natural side effect that occurs as water warms up and cools down. But if that air can’t escape, you’ll get cold patches at the tops of your radiators. Over time, this means it takes more energy to heat your home, which isn’t good for your bills.
How long does it take to bleed a radiator?
The average radiator should only take 20-30 seconds to bleed. This depends on the size of your radiator and how much air needs to be let out of each one.
How often should you bleed your radiators?
To keep your boiler healthy, and your central heating efficient, you should bleed your radiators around twice a year. We also suggest checking every so often for cold patches, just in case.
When should you bleed your radiators?
You can bleed radiators at any time. But it makes sense to do it at the beginning of the heating season to make sure your heating is as efficient as possible.
Should you bleed radiators if you have a combi boiler?
You can still bleed radiators with a combi boiler. But as they work within a sealed system you’ll need to add water back into your central heating system afterwards. You should find detailed instructions on how to do this in your boiler’s manual. If you’re still not sure, call in a professional to bleed them for you.
Is bleeding your radiators the same as flushing your central heating system?
Bleeding your radiators isn’t the same as flushing your central heating system. Flushing removes the buildup of substances that develop over time and affect your boiler’s performance. This is best carried out by professionals.
How to bleed your radiators
Before you begin, you'll need two things to hand:
A radiator key, or flathead screwdriver
Depending on what kind of radiator you have, you’ll either need a radiator key or a flathead screwdriver. Check which you’ll need by looking at the bleed valve - you’ll find it at the top of your radiator on either the left or right hand side.
Old cloths or towels
When you bleed your radiators, a little extra water will come out so you'll need some cloths or towels to catch it. It’s a good idea to put some on the floor too, just in case.
Equipment at the ready? Let's get started.
Step 1: Turn the heating on
The heating needs to be off while you bleed your radiators, but you do need to have it running beforehand so you can spot which radiators have cold spots. These are the ones you need to bleed.
Step 2: Switch the heating off
It’s best to bleed radiators while they’re still a little warm, so turn the heating off and wait for them to cool down a bit. About 20 minutes should do it (just enough time for a cuppa).
Step 3: Prepare for spills
Place the old cloths or towels on the floor underneath the bleed valve to catch any spills.
Step 4: Open the bleed valve
Put the radiator key in the bleed valve and hold a rag around the valve with your other hand. Turn the key anti-clockwise, about half a turn, until the trapped air begins to hiss out.
Step 5: Wait for some water to come out
When a little water starts to trickle out of the bleed valve, that means all the trapped air is gone. Turn the radiator key clockwise to close the valve. Be careful not to over-tighten it, as this can cause damage.
Step 6: Wipe away any drips
If there’s any water around the valve or dripping down the radiator, wipe it away with a dry cloth to prevent rust.
Repeat steps 3 to 6 for every radiator with cold patches.
Want to be more energy efficient?
Bleeding your radiators can help you save energy, and keep your costs down. If you’d like to find out even more about lowering your energy consumption, check out the energy-saving advice section of our website.
Important information regarding our advice and tips
We try to make sure that the information we include in our blog is correct. Unfortunately information can become outdated, and we can’t guarantee that we won’t ever make a mistake.
With that in mind, any activities you undertake as a result of the information contained within this blog is done so at your own risk. We accept no responsibility (including for loss, damage or injury) for your use of the advice on our blog, or the wider website. Please always consult a professional if you intend to carry out DIY and are not fully confident in doing it yourself.