Have you noticed that your radiator isn’t working as well as it used to?

This could be because air is trapped inside the unit, which prevents water from moving around the radiator. A solution to this problem is to bleed your radiator.

What, exactly, does it mean to bleed a radiator?

Bleeding a radiator refers to releasing the air that’s inside the radiator.

It might surprise you to learn that you should bleed your radiator once a year. This ensures that it continues to work at its best.

Luckily, bleeding a radiator isn’t difficult and anyone can do it.

Here’s How To Bleed A Radiator In 5 Easy Steps

Bleed A Radiator

Step One: Get The Items You Need

In order to bleed your radiator, you will need a radiator key and a cloth or rag, as well as a bucket. Safety gloves should also be worn.

Note that you can get a radiator key from a DIY store, or online retail stores such as Amazon.

Step Two: Turn Off The Heat

Switch off your home’s heating system and hot water so that your radiator won’t become hot and make it difficult for you to work on it. It’s also dangerous, as boiling hot water could spray out of the radiator onto you.

Step Three: Release The Radiator’s Air

Take your radiator key and use it to turn the radiator valve. This is located at the top of the unit. The key will need to be attached to the groove located in the centre of the valve. Make sure you turn it anticlockwise.

When you hear a hissing sound, then you know you’re doing it right because this is a sign that the trapped air is being released. Keep your bucket and cloth handy in case any water is also released.

Step Four: Tighten The Valve

Once the hissing is over and you can only see the liquid coming out, then you know you can retighten the radiator valve. You can also turn the central heating back on.

Step Five: Check The Boiler Pressure

Don’t forget to check the boiler pressure by looking at its gauge. It’s possible that bleeding your radiator has caused its pressure to decrease.

If it has pressure that’s too low, you will need to refill it. You can do this by using the tap or lever, which is known as the filling loop.

How do you know that you’ve successfully bled your radiator?

Once you’ve turned on the hot water and central heating in your home, you’ll see that your radiator heats up within a few minutes. The boiler pressure reading should be between one and two bars. Both of these signify that bleeding your radiator has been successful.

Does Your Radiator Need Bleeding?


Although you should bleed your radiator about once a year, it’s not always easy to know when your radiator requires bleeding.

Here are some of the signs to look out for.

The radiator feels cold at the top

If your radiator is warm at the bottom but cold at the top, that means air is trapped inside it and it’s preventing water from circulating around the radiator.

The radiator is cold all over

Instead of the radiator temperature is different in different parts of it, you might find that your radiator is cold, period. There could be trapped air in the radiator pipes that have completely blocked the hot water from entering the radiator.

The radiator is making a noise

If your radiator is making a strange noise, such as rattling or gurgling, this is a sign that the radiator has a problem. You should try bleeding it to see if that sorts it out.

What If You Have To Bleed More Than One Radiator?

Bleeding Radiator

If you have multiple radiators in the home and you want to bleed them all, you can do this at the same time.

However, it’s important to note that you will have to start with the downstairs radiator – the one that’s the furthest distance from your boiler.

Once you’ve bled that one, you can move to the one that’s the second furthest away and so on until you get to the one that’s closest to the boiler.

Since air rises through the heating system, starting from the bottom of your home and moving upwards is a good tip to keep the heating system working well.

What Does It Mean If Your Radiator Is Still Cold After Bleeding?

If you’ve followed the steps on how to bleed a radiator but yours is still acting up and not warming up properly, this could point to a bigger issue.

You should check your thermostatic radiator valve as its pin could be stuck. Remove the head on the valve and you’ll see an exposed pin.

If it’s stuck in position, you will need to use an adjustable spanner to gently hold it and move it up and down. This will loosen it properly so that hot water will be allowed into the radiator.

If that doesn’t work, then you could be dealing with an air lock in the system. You will need to flush out your radiator, but this is a bit more complicated so it would be good to contact a professional plumber.

What Does It Mean If Water Coming Out Of The Radiator Is Dirty?

What Does It Mean

When bleeding your radiator, you might find that the water which comes out is dirty.

Here’s a general guide to keep in mind when you’re bleeding your radiator: if the water is coming out clear and clean, then it’s normal.

If it’s coming out a bit brown, that’s a sign there’s sludge in the heating system and it needs to be flushed out. If the water is a dark brown colour, the problem of sludge is serious so you should contact a professional plumber without hesitation.

What causes sludge to form?

Sludge is basically a build-up of dirt and rust inside the pipes. If it isn’t cleaned away, it can make your heating system work ineffectively, while also damaging it, such as by blocking its pipes and valves or ruining its heat exchanger. These can end up being costly repairs.

You can prevent sludge from accumulating in your central heating system by installing a magnetic boiler filter. This shouldn’t cost you more than £100 and it’s not difficult to install, but you will need to clean it once a year.

This is how a magnetic filter works to prevent sludge: while hot water is sent from the boiler around the radiator and then back to the boiler, a magnetic filter basically steps into this process because it’s installed on a pipe that sends the water back into the boiler, therefore keeping it clean.

How To Maintain Your Heating System

It’s important to ensure that you keep your home’s heating system in good condition, otherwise any trapped air will make your boiler have to work much harder to keep your home warm in the winter.

This will translate into higher energy bills. While it’s important to bleed your radiators regularly, it’s just as essential to ensure you keep your heating system healthy. You can do this in the following ways:

  • Get your home’s heating system serviced by a professional plumber. You should aim to have this done once a year so that any problems with it can be nipped in the bud, therefore decreasing your future expenses.
  • When it’s summer, you should turn on the heating once in a while to prevent the boiler from seizing up and not working when you need it.
  • Check your heating system regularly for any problems, like if the pressure drops very regularly or you can see some leaks. Fixing such problems will help to prevent complications and further damage.

Related Questions

Bleeding Radiator Related Questions

Why do you have to bleed your radiator so often?

If you find yourself having to bleed your radiator very often, this is a sign that there could be a leak in the system, so it’s good to call a professional to check the radiator.

When is the best time of year to bleed your radiator?

You should aim to bleed your radiator before winter. When the heating is on, this will help you find any problems with your radiator much easier and you’ll ensure that it works well to keep you warm when it’s cold.


Although the thought of bleeding your radiator could be an overwhelming one, now that you’ve read this article it’s plain to see that bleeding your radiator is really not a big task.

Anyone can do it, even if they don’t have DIY experience.

In this guide, we’ve also featured important information about why you should aim to bleed your radiator once a year or if it’s showing signs of not working properly.


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