Radiators not getting hot at bottom

[Steveb21]

New radiators installed 12 months back.

With old radiators still on the system was flushed/cycles a few times.

I have noticed some radiators do not get hot enough at the bottom. Also apart from one radiator in hallway I hardly feel any heat off the other radiators - unless I am very close to them.

I have been told that as my property has had a former extension then there is a possibility that the pipe work installed is causing the issue? Something to do with linking the extension are to existing radiator flow rather than installing a new link? (If that makes sense?)

 

[Doggit]

Nope, it doesn't.

Radiators that are cold at the bottom, suggest sludge in them, so was inhibitor put in the system after it was refilled. But if some rads don't get hot at all, then that suggest the rads need balancing as well. What is the temperature of the flow, and are the flow and return pipes to each rad hot.