Wikipedia sometimes has good information on home maintenance items sometimes you need to stop and pause. This is a clip from the heating radiator article – perhaps a little thin.
All “radiant” (ie. heat radiates from hot water) systems need to be bled, or purged of air, on occasion.
If there is air (or other gases such as Hydrogen) trapped inside the radiator, then the water cannot rise to the top, and only the bottom area gets hot.
Often radiators located on upper floors will accumulate more air than ones on lower floors as the air will tend to rise to the topmost point in the system.
Note that if air is getting into the radiators frequently, this may be the sign of a leak somewhere, such as a dripping valve, or loose joint.
See whilst you plumber will know about radiator bleeding the people who contribute to Wikipedia do not always have the full details.
I will do an article on radiator banging and bleeding soon …..
