If you've got the heating on full blast but your radiators feel cold, cold in some parts but warm in others or just not as hot as they should be, it's probably time they were bled.

Bleeding radiators is a simple procedure but one which you have to perform carefully to avoid being scalded by hot water within the system.

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What does bleeding a radiator actually mean?

Essentially, bleeding a radiator means letting trapped air out of it by releasing a bleed screw on the raditator itself.

When should you bleed a radiator?

A radiator needs to be bled when your central heating is no longer warming your home efficiently. When air bubbles become trapped in the radiator's system, hot water is stopped from circulating around the radiator. When air is inside, radiators can get cold spots and appear cold even when they're fully switched on.

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How do I bleed my radiators?

First you’ll need to turn the heating on and check the individual radiators in your property to see whether all their parts are heating up. Upon discovering any cold spots, switch the heating off before beginning to bleed the affected radiators. The radiators will need to be cool enough for you to handle prior to starting.

The opening step is to attach the radiator bleed key - a small spanner that you can buy from DIY stores for a few pounds - onto the square head of the bleed screw in the radiator valve at the top or on the side of the radiator. Some bleed screws also have a groove so that you could use a flat-head screwdriver for this instead.

The radiator bleed key slips onto the square head of the radiator valve screw on the side of your radiator.

Wrap one cloth around the bleed key and hold another cloth at the bottom of the valve as you turn the key anti-clockwise to loosen the screw. When you start to hear trapped air escaping, wait for hot water to travel back up to the valve where your hands are and prepare to turn the key and shut the valve quickly when liquid starts to leak out.

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Once you’ve repeated the bleeding process on all your cold radiators, the final step should be to check the pressure gauge on your boiler. If the pressure reads as being too low, it may require a boost or 'top-up'. This can be achieved by opening a tap on the filling loop of your boiler.

The pressure required depends on particular home heating setup but it is usually between 1.0 and 1.5 bar - the optimum pressure may be indicated by a red needle on the gauge.

Once the system's pressure is set, switch the central heating back on and check your radiators again to see if they’re now heating up correctly.

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