Question from John M Wainwright, via e-mail:
Why do radiators get hot at the top and cold at the bottom?
Answer from Martyn Bridges, director of marketing and technical support at Worcester, Bosch Group:
I would suggest that your radiators are in need of a system cleanse or a flush. It would appear that the radiators are partially contaminated with magnetite or sludge and if the system has never been flushed and treated with an inhibitor then it may be time to do so. A contaminated system is lower in efficiency than a clean system, lower in room temperature levels, as well as potentially reducing the life of the water based components, pump, diverter valves etc.