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How to Bleed Your Radiators – A Step-By-Step Guide

With summer disappearing into autumn, temperatures are starting to drop and it’s likely that you’ll be turning on the heating within the next few weeks. With that in mind, it may be a good idea to perform checks on your radiators.

Bleeding them is part of that process and is a good idea at the start of the autumn. Full radiators can improve the efficiency of your central heating system and cut the amount you spend on energy bills.

But what exactly do we mean by “bleeding a radiator”?

What Does Bleeding a Radiator Mean?

Simply put, when you bleed a radiator, you let out any air that has become trapped within. When air becomes trapped in radiators it prevents water flowing through the whole surface area, resulting in cold spots.

This is also one of the best ways to detect trapped air. By running your hands across the surface of the radiator moving from bottom to top, if the top section of the radiator is cold compared to the bottom half, it’s likely that trapped air is the cause.

Fortunately, there’s an easy fix for radiators with air trapped within them which is known as “bleeding” the radiator.

How to Bleed Your Radiators

Firstly, you’ll need a radiator bleed key. The only other equipment you’ll need is a small Tupperware or old cloths/towels to catch any water as it runs out of the top of the radiator.

Next, you need to turn your heating up to make sure all radiators come on, revealing any cold areas. Proceed to check each radiator individually for cold spots. Similarly, if you can hear gurgling or your radiator takes an unusually long period to warm up, these are also signs of trapped air.

Once you’ve identified the radiators that require bleeding, it’s a good idea to turn the heating off so that you don’t accidentally scold yourself with hot water when bleeding.

At each radiator prepare the area first by either lying down old clothes to protect flooring or having a container ready to catch any run off. Then take the radiator bleed key, and insert it into the bleed valve which is found at the top of the radiator, to the side. It looks like a round hole with a square inside. Once locked together, carefully turn the valve anti-clockwise – as the air begins to escape you’ll hear a hissing sound.

A quarter to half a turn will be enough, never open the valve fully because once you bleed air from the radiator water will come rushing out. Continue this process, holding the radiator bleed key until the air stops coming out. When water begins to flow out from your radiator bleed valve, then you have completed the bleeding process. Turn the bleed valve clockwise to seal the radiator; taking care not to overtighten.

Repeat this process for all of the radiators in your house that require bleeding. Once you’ve completed the bleeding process on all of the necessary radiators, you can turn on the heating once again to ascertain the difference it’s made to the heat emanating from your radiators.

Finally, you may need to re-pressurise your heating system. When you bleed a boiler heating system you always lose some water, and the pressure will likely drop as a result. For reference,the pressure in a typical family home is usually between 1.0 and 1.5 bar.

To re-pressurise, you’ll need to locate the central filling loop connected to your boiler. It looks like a tap and is connected to your main water supply. Turn the tap very slowly to add pressure back into the system; taking care not to over-pressurise.

Not all Cold Spots Can Be Fixed Through Bleeding

Whilst trapped air within radiators can be easily fixed, cold spots on the bottom half of your radiator may indicate more serious issues such as corrosion, blockages, and build-ups of debris. In these instances, a power flush may be required to remove harmful substances from your central heating system.

If you think that your radiators have more severe issues than trapped air, then don’t be afraid to call our advice line on 020 323 5678 to receive free and impartial advice regarding the best course of action.