How to guides - Radiator cold spots

From time to time our radiators within our home can develop cold spots, these can quite often be just at the top of the radiator or sometimes just at the bottom. Depending on where the cold spots are located on the radiator can mean different things. A correctly working radiator should be hot all over.

If you find your radiator to be cold at the top, this is usually just a sign that there is trapped air within the radiator itself. This can be quite easily resolved by bleeding the radiator to release the air from the system. This can be done by opening the bleed valve with the key, if air is trapped within the radiator you will hear the air escaping with a hissing noise.

It is always a good idea to keep a small jug or container near the valve to catch any water which will leak from the valve once all the air has been released. At this point close off the bleed valve and ensure it is fully tightened. Once any radiators have been bleed, you must ensure that the boiler pressure is topped back up to between 1 and 1.5 bar as by bleeding the radiators you have released pressure from the entire heating system.

For more information on how to top up your boiler please view our how to guide here.

If you have found your radiator to be cold at the bottom, this unfortunately could be a sign of sludge building up in your radiator and heating system. Sludge within your heating system will eventually prevent the hot water from circulating correctly around your heating system.

As the sludge builds up over time, it can also cause blockages within your boiler which may result in parts being damaged. Sludge can occur over a period of time and is a build up of rust and limescale debris which can collect at the bottom of your radiators and in small pipes and parts of your boiler. If this does occur depending on the severity of the problem and the amount of sludge build up, a power flush might be recommended. This should be done by a professional engineer.