How to Bleed a Radiator | AMW Heating
How to Bleed a Radiator Bristol Plumbing

Posted on |

How to Bleed a Radiator

As we move into Autumn and then Winter, the temperature will begin to drop and your heating will begin to kick-in. One of the most common issues that can arise is a radiator that isn’t heating up properly: the bottom half is hot but the top half is cold!

More often than not, the solution is simple: the radiator needs bleeding.

Bleeding a radiator might sound daunting, especially if you’ve never done it before, but it’s a straightforward task that can save you money and keep your home warm and cosy. Here, we will walk you through the steps on how to bleed a radiator safely and effectively.

Why Bleed a Radiator?

Over time, air can become trapped in your radiators, causing them to heat unevenly or not at all. You might notice that the top of the radiator is cold while the bottom is hot, or that the radiator makes gurgling or banging noises. Bleeding your radiators releases this trapped air, allowing hot water to fill the entire radiator and heat your home efficiently.

What You’ll Need

Before you start, make sure you have the following:
Radiator key (available at most DIY shops like B&Q or Wickes)
A cloth or towel
A container or small bowl (to catch any drips)
Protective gloves (optional, but useful for preventing burns)

Step-by-Step Guide How to Bleed a Radiator

Turn Off Your Heating
Before you start bleeding your radiators, it’s crucial to turn off your central heating system. This prevents hot water from circulating while you’re working and reduces the risk of burns. Wait for the radiators to cool down before proceeding.
Locate the Bleed Valve
The bleed valve is usually found at the top of the radiator, on one side. It’s a small valve with a square or hexagonal shape, which is where you’ll use the radiator key. Place a cloth or towel beneath the valve to catch any water that may escape.
Insert the Radiator Key
Insert the radiator key into the bleed valve. Hold the key with one hand and have your container ready in the other.
Turn the Key Anti-Clockwise
Slowly turn the radiator key anti-clockwise (to the left). You should hear a hissing sound as the trapped air escapes. Keep turning until water starts to trickle out steadily. Once water starts to flow, it means the air has been completely expelled.
Close the Valve
As soon as water begins to flow, turn the key clockwise (to the right) to close the valve. Be careful not to overtighten it – just a snug fit will do. Wipe away any drips with your cloth.
Check the Boiler Pressure
After bleeding your radiators, it’s a good idea to check the pressure on your boiler. Bleeding can sometimes cause a drop in pressure. If necessary, top up your boiler’s pressure to the recommended level, usually between 1 and 2 bars, depending on your system.
Turn Your Heating Back On
Once you’ve bled all the radiators (start with the ones closest to the boiler and work your way out), turn your heating back on and check that they are warming up evenly. The entire radiator should now be warm from top to bottom.

When to Bleed Your Radiators

You should bleed your radiators at least once a year, ideally before the start of the heating season. However, if you notice cold spots or hear unusual noises, it’s worth checking whether bleeding is necessary.

Final Tips

  • If you find that you’re regularly needing to bleed your radiators, it may indicate a more significant issue with your heating system, such as a leak. In this case, it’s best to contact a Bristol Plumber like the team at AMW Heating.
  • Always start with the radiators on the ground floor and work your way up if you live in a multi-storey home.
  • Consider wearing gloves, especially if the radiator is still warm.
  • Bleeding your radiators is a simple yet effective way to keep your heating system running smoothly. With just a few minutes of effort, you can ensure that your home remains warm and comfortable throughout the colder months. So, next time you notice a radiator not doing its job, don’t hesitate to give it a quick bleed!

Still not sure?


If you would like further help with your radiators (or other aspects of your heating system, including your boiler or water tanks) please contact AMW Heating for help. You can give us a call on 0117 990 2735, or email us at info@amwheating.co.uk or contact us here.