Radiators not as hot as they used to be? It's bleeding time you bled your radiators. It's easy. Here's how.
How do you bleed a radiator quickly and easily? Don’t worry, they won’t be in any pain!
If your radiator is feeling cold or has cold spots, it’s probably time to remove trapped air by bleeding it.
In this simple, step-by-step guide, we’ll show you exactly how to do it and cover some of the most frequently asked questions.
When should you bleed your radiator?
Over time, air and/or sludge and other debris can build up within the central heating system, and this can result in characteristic cold spots in your radiators.
When these cold spots develop, it’s likely that the time has arrived for you to release this trapped air by bleeding your radiators.
These are some of the most common signs that it’s time to bleed your radiators:
Radiator cold at the top?
If the top of your radiator is cold when turned on, then this is a common sign there is trapped air in the radiator that’s preventing the hot water from being evenly circulated.
In order to fix this, the trapped air needs to be released so that the radiator can be heated evenly. Cold patches in your radiators are a sure sign that it’s time to bleed them.
The entire radiator is cold
If your entire radiator is cold then this may also be a sign that there’s trapped air in your central heating system, but likely the pipework leading to your radiator, rather than the radiator itself.
Radiators are making noises
A noisy boiler or noises in your central heating system can have various causes, but characteristic gurgling and rattling noises are a sign of trapped air in the radiators.
Regardless of the cause, often the first port of call will be to bleed the radiators to see if the issue is rectified. If not, the issue may be more complicated and require diagnostic assistance from a registered Gas Safe Engineer.
What do you need to bleed your radiator?
In order to bleed your radiator, you will need some basic equipment, but don't worry, you’ll likely have most of it in your home already.
A bucket
A radiator key
Cloth or rag
Safety gloves
Important note: Make sure you allow your radiators to cool down before bleeding them, or otherwise use safety gloves.
How to bleed your radiator - step by step guide
Check out our video on how to bleed a radiator here:
Follow these steps to get your radiator bled fast and easy:
Step 1 – Prepare the area
Bleeding your radiators can be extremely messy, so you will want to protect your floor before you begin. Lay down some old towels or a rag just below the radiator, you are going to bleed. It’s also a wise idea to wear old clothes that you aren’t too bothered about getting messy.
Step 2 – Allow your radiators to cool down
Ensure your radiators are cool before you proceed with the bleeding, therefore, ensure your heating is off, and you wait long enough before you begin the process.
Step 3 – Open up your thermostatic radiator valve
It’s always advised to start bleeding the radiator at the lowest point in your property, e.g. downstairs rather than up. Once you have located this radiator, it’s time to fully open up the thermostatic radiator valve, which you can easily do by turning it to the highest number on the dial.
If your radiators do not have thermostatic radiator valves, simply make sure the lock shields are open.
Step 4 – Open up the bleed vent
Next locate the bleed vent, also called the radiator valve, this is usually at the upper right-hand side of the radiator. Once you have found this, insert the bleed key and turn it anti-clockwise.
You should first hear air escaping before water starts to leak from the valve. Let out a small amount of water from each radiator. Have a bucket at the ready to catch any of the water.
Helpful tip: It’s a good idea to place a tissue or cloth just below the bleed valve as you first open it up. This will help catch any dirty water as it leaks and hopefully prevent any of that dirty water from splattering walls or other surfaces.
Step 5 – Close the vent and repeat
Once you have bled the radiator, it’s time to close the vent. It’s important not to over-tighten it as this could result in damage.
You can then continue the process on each of the radiators in your home, remembering to start with those at the lowest point in your home i.e. you would do the radiators downstairs and then proceed to those upstairs.
Step 6 - Check the boiler pressure
If you have a boiler and central heating system that is pressurized, then bleeding the radiators will have likely result in a drop in pressure and you will need to top it up.
You can check your system's pressure by looking at the boiler’s pressure gauge. If it is within the normal green range i.e. between 1 and 2 bars, you won’t need to do anything. However, if it’s too low (below 1 bar), you’ll need to repressurise the system.
If the pressure is normal, then you can turn your heating on and check if bleeding the radiators fixed the “cold spots”.
You can check our complete guide on fixing high boiler pressure or our guide to topping up boiler pressure here.
Bleeding radiators FAQ
Here are some of the most common radiator bleeding questions and answers:
How often should you bleed your radiators?
Ideally, you should check and if necessary, bleed your radiators every couple of months.
However, it’s especially important to do it before the winter months set in, so you can ensure your heating is in full working order before the time comes when you will need it most often.
How do I know if bleeding the radiators has worked?
Once you have finished bleeding all the radiators in your home and have checked to see if your system's pressure is in the normal range, you can switch your heating back on.
If the issue was caused by trapped air, then you should find your radiators radiate heat evenly and that the cold spots have now gone.
Is your radiator still cold after bleeding?
If your radiator is still cold or has “cold spots”, even after being bled, then it’s likely that there is another cause for them and it’s not related to trapped air.
These are some of the other common potential reasons that may be causing cold radiators:
Thermostatic radiator valve problems
Is one of the thermostatic radiator valves broken? If one of the pins is jammed and unable to open at all or only partially, it may prevent enough hot water making its way into the radiator.
Get your central heating system flushed
Over time rust, debris and dirt can build up inside your central heating system and lead to the development of sludge.
This thick, black/brown substance can result in blockages in your system, cause corrosion and prevent hot water from evenly circulating through your radiators, resulting in the familiar “cold spots”.
To get rid of this sludge and prevent it from building up, it’s recommended to get your system flushed every 5 years.
There are a few types of flushes, which you can read about in our power flush guide. However, ultimately, they all work by removing the sludge using high pressure and a combination of chemicals.
Note: Heatable includes a chemical flush and Adey magnetic filter with all new installs as standard, but you can upgrade to a ProFlush (magnacleanse) if you want an extra deep clean of your heating system.
Do you need to balance your radiators?
If you have bled your radiators and had your system flushed, but you are still experiencing a cold spot in a particular radiator, it may mean that the hot water from your boiler is not being evenly distributed to all your radiators.
This may mean that your radiators may need to be balanced i.e. make the water flow evenly from your boiler to each of the radiators in your home.
Here's our complete guide on balancing radiators.
For instance, if the radiator furthest away from your boiler is the one that is failing to heat up, it’s a reliable sign that your radiators need balancing.
Add chemical inhibitors
Over time, a variety of deposits can build up within your central heating system (including your radiators), including dirt, rust, and sludge.
If left to linger, these deposits can result in corrosion of major components, resulting in leaks and damage that can lead to significant repair work.
Even worse, sludge can deposit within your radiators, leading to blockages, cold spots and make your systems pump work even harder to circulate the heating water.
Rust inhibitors can help prevent corrosion, so it’s recommended that you add them to your system and top them up regularly.
Can you bleed your radiator when the heating is on?
There are two major reasons why you should not bleed your radiator when the heating is turned on and active.
Firstly, the hot water is a hazard and will potentially spray and lead to burn injuries. Secondly, if the central heating pump is active, releasing air at the same time may actually draw more air into the system.
For these reasons, it’s important to only bleed your radiators once the heating has been turned off and enough time has been given for the hot water to cool.
Related reading:
Think you may have a boiler problem?
Do you think you may have another issue not related to trapped air in your central heating system or radiators?
If so, you may want to check out our guide to the most common boiler problems (and solutions).
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