Cold radiators? How to bleed and balance your central heating

Radiators that never get properly hot are one of the most common heating complaints. The pattern of the cold spot usually tells you what is wrong.

Cold at the top, warm at the bottom

This usually means air is trapped in the radiator. Bleeding it should fix the problem.

1. Turn the heating off and let the radiators cool.

2. Hold a cloth under the bleed valve at the top corner of the radiator.

3. Turn the valve slowly with a radiator key until you hear hissing.

4. Close it as soon as water appears.

5. Check the boiler pressure and top it up if it has dropped.

Cold at the bottom, warm at the top

This often points to sludge settling in the radiator. A chemical cleanse, or a power flush for badly affected systems, may be needed.

Some radiators cold, others hot

If radiators nearest the boiler are hot and those further away stay lukewarm, the system probably needs balancing. Balancing means adjusting the lockshield valves so that hot water is shared evenly around the house. It takes time and a thermometer, and an engineer can do it as part of a service.

The whole radiator is cold

• Check the thermostatic radiator valve is turned up and not stuck. A stuck pin can often be freed gently.

• Check the lockshield valve at the other end is open.

• If several radiators are cold, the pump or a diverter valve may be the problem.

Need help with your heating?

The Essential Connection fixes heating problems across Walton-on-Thames, Weybridge, Cobham, Esher, Kingston and South West London. Get in touch or call 07719 664615.