I have a conventional boiler and a gravity fed hot water system with cold water tank in the loft, hot water tank on the first floor and gas fired boiler on the ground floor.
When I put the heating on only the first 5 rads on the run heat up. On the 6th the pipe to the lockshield valve is hot as is the valve itself, but the rad is stone cold as are the remaining three rads on the run.
I have checked that all the lockshield valves are fully open on all rads and the thermostatic valves are set to the max and all rads have been bled. I am not sure whether there may be a block in the rad or something like that?
Grateful for any advice?