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How to Bleed a Radiator
Bleeding a radiator is an easy job you can do yourself in just a few minutes, and it could help you avoid the cost of hiring a plumber to bleed a radiator. This guide will show you step-by-step, and it also includes the tools and materials you'll need to do it.
Table of Contents
Benefits of Bleeding Your Radiators
Regularly bleeding your radiators can help your heating system run more efficiently. Removing trapped air lets hot water circulate properly, so your radiators heat up faster and more evenly.
This can also help to:
- Lower your heating bills, as fixing system inefficiencies helps your boiler use less fuel.
- Reduce strain on your boiler's pump, as less trapped air means less internal corrosion over time.
- Help prevent noisy gurgling or banging from your pipes.
How Do You Know When to Bleed Radiators?
Turn on your central heating and carefully feel the surface of each radiator once they've heated up. If it's hot at the bottom and cold at the top, there's trapped air inside and it needs bleeding.
Other signs to look out for include:
- Gurgling, banging, or whistling noises from the radiator or pipes.
- The radiator takes longer than usual to heat up or the room feels colder despite the heating being turned on.
- Higher energy bills due to your boiler having to work harder.
If you notice any of these, turn off your heating and let the radiator cool before you bleed it.
What Tools Do I Need to Bleed a Radiator?
Before we start, what is "bleeding a radiator"?
Radiator bleeding is the process of removing trapped air from your radiators to improve the flow of hot water and stop cold spots from forming in your radiators.
So, what do I need to bleed my radiators?
Here's a list of the tools you'll need to bleed a radiator:
- Radiator key
- An old cloth
How to Prepare to Bleed a Radiator
There's no specialist safety equipment needed to bleed a radiator, but keep an old cloth to hand, as water and sludge can spit out during the process.
Before you start, you should:
- Turn off your heating and let the radiators cool down.
- Keep an old cloth to hand to catch any spraying or dripping water when you turn the radiator key.
How to Bleed a Radiator Yourself
If you're installing a new radiator in your home, bleeding your new radiators once they've been fitted will be an important step in your process.
So, how do I bleed my radiators?
Here's what you need to know:
Step 1
Run your hand over the radiator to check if it is cold at the top or bottom.
If it's cold at the top, that means there is air trapped in the radiator, and that it needs to be bled.
Step 2
Begin by turning off your central heating, and allow your radiators to cool.
Step 3
Next, place an old cloth underneath the valve to catch any water that may drip out during the bleeding process.
Step 4
Use the radiator key and turn it anti-clockwise about a quarter of a turn until the air stops, and the water runs smoothly out of the valve.
Step 5
Then, turn the valve off again by turning it clockwise.
Step 6
You can then turn your heating system back on, and the problem should be solved.
My radiator bleed valve is stuck. What can I try?
"Give it a gentle tap with a hammer then try turning it. Make sure the 2 valves on the radiator are turned off first."
What to Do After Bleeding a Radiator
Once you've bled your radiators, check your boiler's pressure gauge. It's normal for the pressure to drop slightly, so top it up using the filling loop if it falls below 1 bar.
Turn your heating back on and check each radiator again. It should now feel evenly warm from top to bottom, with no gurgling.
The water that comes out during bleeding is sometimes dark or murky, which can be a sign of sludge building up inside the system.
Why is the water black when I bleed my radiators?
"Usually a sign of an aged system with possibly little or no inhibitor concentration. It can be caused by too much raw water or incorrect pipe layout. It would be recommended to get the system water inspected and tested."
If your radiators are still cold in places or need bleeding often, it could be worth having your system checked by a heating engineer.
Does Bleeding Work the Same for All Types of Radiators?
Most radiators are fairly similar to bleed, but the valve itself can vary.
- Older radiators usually have a square bleed valve that needs a radiator key.
- Modern radiators often have a slotted valve you can open with a flathead screwdriver.
- Some designer or column radiators have the valve tucked at the side or back, so check the whole radiator if you can't find it straight away.
- Towel radiators and underfloor heating systems may need bleeding at a manifold rather than a single valve, so it's worth checking the manufacturer's instructions first.
If you can't find a bleed valve on your radiator, it's worth asking a heating engineer to take a look.
FAQs
Can You Bleed a Radiator Without a Key?
Yes, you can bleed some radiators without a key. For example, if your bleed plug has a small slit in the middle, you can open it with a flathead screwdriver.
Can You Bleed a Radiator When the Heating Is On?
No, you should turn your heating off before you bleed a radiator, and wait for it to cool down first. If you open the valve while the system is hot, the water and air inside could scald you.
Which Radiator Should You Bleed First?
Bleed the radiator furthest from your boiler first, then work your way through the rest of the house. This allows air to move through the system and escape properly. If your boiler is downstairs, start with the top floor radiators before moving downstairs. Air travels to the highest and furthest points in a heating system, so the radiators upstairs typically contain the most trapped air.
Why Bleed Radiators?
When air gets trapped in radiators, it causes cold spots, and the radiators don't heat up as they should. Bleeding them (removing the trapped air) fixes this issue, allowing the hot water to circulate as normal.
When Is the Best Time to Bleed Radiators?
You should bleed your radiators at the start of the heating season. This allows you to check your system is fully functional without any trapped air before you come to use it. It's also worth checking them again partway through winter, as air can build up over time. Most homes only need this done once or twice a year.
How Long Do You Bleed a Radiator For?
This varies depending on the size of your radiator and the amount of air trapped inside. It usually takes around 20 to 30 seconds to bleed a radiator, but some larger radiators could take up to a minute.
Does Bleeding a Radiator Cause Your Boiler to Lose Pressure?
If you've recently bled your radiator, you may notice a small loss of pressure. You can easily top this back up using the filling loop.
Why Is My Radiator Still Cold After Bleeding?
If your radiator is still cold after bleeding, sludge or debris could be blocking the system. Check your boiler pressure and top it up if it's low. If the radiator is still cold at the bottom, you may need a power flush from a heating engineer. If it's an old radiator that keeps having issues, you may want to look into the cost of replacing it instead.
What's the Difference Between Bleeding, Flushing and Balancing a Radiator?
Bleeding removes trapped air from a single radiator. Flushing clears sludge and debris from the whole heating system, typically with a power flush. Balancing adjusts the flow of water between radiators so they all heat up at a similar rate. If your radiators need frequent bleeding or heat unevenly even after bleeding, a power flush might be worth looking into.
What Happens If You Don't Bleed Your Radiators?
Without bleeding your radiators, you run the risk of having higher heating bills, lower efficiency, and cold rooms.
Do You Need to Bleed All Your Radiators If Only One Needs It?
No, you only need to bleed the radiators that feel cold at the top or are making noises. It's worth checking each one while you're at it, though, as trapped air can build up in more than one radiator at a time.
