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How to bleed a radiator in 6 easy steps

Is your radiator making clicking noises or struggling to warm up or cool down? Then you probably need to bleed your radiator. Find out how to bleed a radiator in this guide.

Due to the nature of the air, pockets can enter your central heating system and cause issues. The air often collects at a point furthest from the boiler, which causes your radiator to be both noisy and cool, even when the heating is turned on.

Bleeding a radiator will release any collected air and allow an even distribution of heat throughout the system. Check out our guide for how to balance a radiator if you want to evenly distribute heat between each of your central heating radiators.

What tools do I need?

  • Just a radiator key. This should cost no more than £3.
  • A towel or two and a bowl – just in case any water escapes.
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How to bleed a radiator system

Step 1. Start with a sense test

Leaking radiator after being bledWhen the heating is on, touch the radiator in question. If it feels considerably cooler at the top than at the bottom, it’s likely that the top is full of air that’s preventing hot water from fully filling the space.

Step 2. Let your radiators cool down

Turn off your central heating and let the radiator cool down. When you bleed a radiator, you run the risk of water escaping. So, to prevent injury, cooling your radiators makes any escaping water run cold rather than scorching hot.

Step 3. Protect the area

Once the radiators are cool, locate the release valve, which looks like a square pin. Protect both the wall and floor around this release valve.

Step 4. Insert the radiator key

Insert the radiator key you’ve purchased from your local hardware or DIY shop into the release valve and turn it until you hear a hiss. Keep the key turned and prepare to turn it back.

Step 5. Turn it off once the water rises

As the hiss starts to subside, you’ll start to hear water move through the radiator. As it rises, it’ll head towards the release valve. The aim is to keep as much water inside the radiator as possible. So, as the water starts to gurgle, get ready to close the valve. Turn the key and shut the valve when you feel like the water is just about to escape.

Step 6. Check the pressure on your boiler

Following the bleed, check the pressure on your boiler. If it needs any adjustment, consult your boiler manual or speak with a local plumber or heating engineer to re-pressurise.

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How to bleed a towel radiator

Learning how to bleed a heated towel rail is similar to learning how to bleed a radiator. They often have the same components that require the same treatment to fix. Both central heating radiators and heated towel racks suffer from a build-up of air that stops them from working to their fullest extent.

So, to get started, you’ll need a radiator key, a towel, a spanner and some old rags to mop up any water spillage. Once you’re equipped, follow the steps below.

Step 1. Turn off the heating and let your towel radiator cool down

Turn off your central heating and wait around 30 minutes for the water inside the towel rail to completely cool. (This prevents you from scalding yourself!)

Step 2. Use your spanner to open all the valves

Make sure all the valves on your towel radiator are open. This includes the thermostatic and lock-shield vales. You’ll need to remove any caps and open them anti-clockwise using your spanner.

Step 3. Find the bleed valve and turn it anti-clockwise

The bleed valve on your heated towel rail is usually at the top or the back. You’ll know it’s the right valve because the screw tends to be square or hexagonal.

Once you know which one it is, use your rag to cover the area around the bleed valve. Then, take your radiator key and slowly turn it anti-clockwise until you hear a loud hissing noise. This means it’s working.

Step 4. Let all the air out

Keep the key turned until all the air has left the towel radiator. Water should follow, which you need to catch in the rag. But if no water comes out and the sound of air stops, you’ll need to top up the water using the filling loop.

Top tip: After you’ve bled your heated towel rack, check your boiler’s water pressure and follow the instructions to top it up if needed. Some boilers do this automatically.

How to bleed a towel rail with no bleed valve

It’s incredibly unlikely your heated towel rail won’t have a bleed valve unless there’s been a manufacturing error. If you can’t locate your bleed valve, try using a mirror to view the back of the unit and see if it’s there.

Some valves are hidden under panels and caps too, so use a flathead screwdriver to flick those off and see if the bleed valve is hiding under those. There’s no way to bleed a towel rail with no bleed valve without breaking the unit or drilling through it and making repairs afterwards.

If you locate a worn valve, use our how to change radiator valves to guide your DIY repairs.

Alternatively, why not hire a Checkatrade member that your neighbours recommend? Our guaranteed professionals offer you greater peace of mind and local expertise that’s worth waiting for.

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How to bleed a radiator without a key?

How to bleed radiators without keys is fairly similar to those with keys. However, you use an adjustable wrench or spanner to turn the valve instead. Again, listen for the air leaving the radiator and tighten it back up at the point the water is about to escape.

How to bleed a radiator if the valve is worn?

Consider emptying your radiator and replacing the valve, which is relatively cheap and easy to install. When emptying a radiator, make sure you have adequate vessels available for the removal of water. It’s also worth hiring a qualified plumber to assist you, as they can ensure the heating is adequately pressurised when complete.

Alternatively, if the bleed valve is worn, consider turning it with a wrench or a screwdriver instead of a radiator key.

How to bleed a radiator with a screwdriver?

A bleed valve is shaped to make it easy to bleed without expensive tools. A radiator key is very cheap, often under £5. However, if you can’t find one of these, something as simple as a flat-head screwdriver will suffice. Find the small gap in the middle of the bleed valve and turn it the same way you would using a wrench or radiator key.

How to bleed a radiator without a bleed valve?

Not all radiators have an easy-to-use bleed valve. However, most radiators are likely to have something that lets air escape. For example, sometimes a valve can be found on the back of the radiator. Look all around the radiator, as sometimes they’re installed upside down!

How to bleed a towel radiator?

If you find that your heated towel rail is not heating up correctly, maybe warm at the bottom and not at the top then you may need to remove air from the rail. Coming shortly is our how-to guide on how to bleed a towel radiator safely.

How long does it take to bleed a radiator?

This can be a very quick easy job to complete if you know what you are doing. Actually releasing air from the valve will only take about 30 seconds. Still, you may find yourself needing to bleed several radiators, chasing the air out of the system, moving from radiator to radiator and starting on lower floors working your way to the top radiators in the house. Air will rise through the system so you need to work methodically.

Do I need to speak to an expert though?

A heating engineer may well be able to advise on correct boiler pressures. So, for a small fee and a basic call-out charge, they might be worth consulting.

How to bleed a radiator combi boiler?

Bleeding a radiator combi boiler involves the same process as above. Follow the step by step guide. If you’re at all unsure, then get a professional in.

How to bleed a traditional towel radiator?

The same principles we’ve outlined above can be applied when it comes to bleeding a traditional towel radiator.

Was this helpful? If so, we have more where this came from. Check out our blog for more how-tos, DIY ideas and inspiration. 

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