A while ago my heating system was changed from an open system with a header tank to a sealed, pressurised system.
Last week a radiator in the bathroom sprung a leak so I decided to replace it. Well, long story short, I called in a Plumber (lack of tools, lack of confidence and lack of strength, in no particular order - me, I mean, not the Plumber!) who recommended changing the valves along with the rad. This needed the system to be drained, so he found the stop c*ck and did so.
It didn't seem to take very long to drain down and despite the drain point being at the lowest elevation none of the downstairs radiators drained out. On completion of the job, he opened the c**ks on the filling loop, re-pressurised the system and turned the boiler on again. To my surprise, none of the radiators either upstairs or down needed bleeding - apart from the new one - either then or now.
I understood how the old gravity system worked, but I am struggling a bit with the sealed, pressurised system that I have now.
Firstly, why did so little water run out when he "drained the system"? And if the system is pressurised, why doesn't the hot water come out of the taps at the same rate as the cold does?
Please?