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How To Bleed A Radiator?

How to Bleed a Radiator?

If your heating is switched on, but your radiators are cold to touch, then there is a good chance it is time to bleed your radiators. Although this might sound drastic, it is a straightforward process you can do yourself, without the need for a qualified heating engineer.

This guide will first, explain why you might need to bleed your radiators, before taking you through exactly how you go about doing it.


What does bleeding your radiator mean?

Bleeding a radiator means releasing trapped air from the system, allowing hot water to flow freely and evenly, thus maximizing its performance. When air becomes trapped in a radiator, it can cause cold spots and reduced heating efficiency.

By using a small brass radiator bleed key to open up the radiator bleed valve, you can release the trapped air, enabling hot water to reach all parts of the radiator and heat up your room more efficiently

How do I know if my radiator needs bleeding?

To know if your radiator needs bleeding, you can follow these steps:

1. Turn on your heating and wait for it to warm up.

2. Feel each radiator. If it’s hot at the top and cold at the bottom, it needs bleeding.

3. If you notice cold patches, dampness, or unusual noises around the radiator, it may also need bleeding.

Bleeding your radiators regularly helps remove trapped air, allowing hot water to flow freely and evenly, thus maximizing the system’s performance.

It’s recommended to bleed your radiators every few months for optimal heating efficiency, and especially after long periods without use, such as at the end of summer.

Why would you need to bleed a radiator?​

Your radiators will need bleeding when air gets trapped inside of them. This trapped air will then stop the hot water from circulating around your radiator, resulting in cold patches.

When your radiators are not working to their full potential, they will not be able to heat your home up as efficiently. Your natural response to this might be to turn the heating up. However, this will only negatively impact your energy bills.

That’s why it is important to solve the root cause of the problem and bleed your radiators. This will make your home heating system work more efficiently, allowing you to save money.

How do you bleed a radiator?

Before you get started, you must first ensure that you have the required equipment to bleed your radiators.

To begin with, you will need a radiator key. Most modern radiators have the same type of valve that will fit with a standard radiator key. If you do not have one, then you will be able to buy one from any DIY shop. It will also be helpful to have some rags and old towels to hand, as bleeding your radiator will inevitably cause some water spillage.

Turn on your central heating

For the first step, you will need to turn on your central heating to find the radiators that are failing to warm up properly. Remember, cold patches are a sign that a radiator is struggling to circulate the necessary hot water.

This step is important because trying to bleed a radiator that does not have any trapped air, will cause water to spill from it as soon as you open the valve. This can drastically lower your boiler’s water pressure, potentially causing your whole system to fail.

Turn off your central heating

When you have discovered which radiators need bleeding, you should turn your central heating off. This is down to the fact that bleeding your radiator with the heating on, could cause boiling hot water to burst out of the valve when the air comes out.

Lay down towels to protect against water

As it is normal for water to spill out of the valve when you bleed your radiators, you should think about laying down old towels on the floor. This will stop the escaping water from damaging your floors or carpet.

Bleed your radiator

Attach the end of your radiator key to the square slot in the centre of the valve. Once they click together, turn the key in an anti-clockwise direction. If the valve is tight, then you can use a rag to help grip the key.

When the valve opens you will hear a hissing sound, which is the air in the top of the radiator starting to escape. The water will now have room to rise, meaning that you should close it quickly, to avoid as much spillage as possible.

Repeat on all radiators

When you have finished bleeding the first radiator, you can repeat the process on all the other radiators in your home that require bleeding.

Check the pressure on your boiler

Bleeding your radiators is always going to involve some water loss. As this can cause the pressure in your heating system to drop, you need to check your boiler’s water pressure.

To check your boiler’s pressure, you need to find the pressure gauge on the front of the boiler. With a hydraulic gauge, the needle will fall below one bar if there is a lack of pressure, while a digital gauge will indicate an issue with the pressure, through a flashing warning.

Considering a boiler upgrade?

Thinking about giving your boiler an upgrade but feeling a bit put off by the upfront cost? No stress! The UK government has rolled out a Boiler Upgrade Scheme that’s got your back. And guess what? Warma UK is here to make the journey smoother for you.

This scheme is a game-changer, offering a helping hand to those wanting to switch to greener and more efficient heating systems without the financial headache. Whether it’s air source heat pumps, ground source heat pumps, or even biomass boilers for some rural spots, there’s a grant with your name on it.

Click on the link below to check whether you are eligible for a free boiler upgrade.

See if you're eligible for free boiler upgrade

See if you're eligible for free boiler upgrade

Michael Cornish