Radiators hot upstairs, cool downstairs

Hi there,

This seems to be a common problem judging by the number of posts in the forum, but none of those already posted seem to fit my scenario.

Gloworm boiler with 8mm pipework. 2 rads upstairs working fine and 4 rads downstairs, only one of which, nearest to boiler/pump, heats up to normal temperature. The remaing 3 all have a very hot feed pipe but the rads only get to luke warm after a prolonged period of time, say 45 mins. The return pipes from these rads are cold. One of these cool rads is brand new, repositioned in room on an extension to original pipework - so no blockage in rad. The problem existed before rad was replaced. System has been drained and re-filled twice - no black sludge to speak of was noticed. All rads have been bled.

My next thought was to look at the manifold for bloackages - but thought it would be useful to raise here - any advice / guidance greatly appreciated.

If you want a permanent solution repipe with 15mm

have to agree, small diameter sytems are a nightmare sometimes. If re piping is an option run as much as you can with 22mm and the rad runs in 15mm. As a rule of thumb only pipe three rads at maximum off a single 15mm flow and return loop