Central heating that reaches every room.

A radiator cold at the top has air in it, and bleeding it usually fixes the problem. A radiator hot at the top and cold at the bottom has sludge, mostly black magnetite from steel radiators slowly corroding from the inside, and bleeding will not help. That needs a clean, then a magnetic filter and inhibitor to stop it coming back.

Uneven heat is often a balancing problem rather than a broken part. Water takes the easiest route, so the radiators nearest the boiler take most of the flow and the far bedroom gets what is left. Tall Georgian and Victorian townhouses, with long pipe runs over four or five floors, show it most. Setting each lockshield valve carefully, with a thermometer, fixes more cold rooms than people expect.

In Victorian and Edwardian terraces we often find radiators sized for draughty rooms that have since been insulated, or one small radiator under the window of a large bay-fronted room. Sizing radiators to each room’s heat loss matters even more if a heat pump is in your future, because heat pumps run at lower temperatures.