Last rad cold

14 Oct 2010
Reaction score
United Kingdom
Ok so I drained and flushed my whole central heating system. The system had 3 drain valves which I drained and also drained all the rads.

All went well but the last rad won't heat up. All rads are bled and the drain valve below the last rad runs hot water, so it's going through the rad with the drain valve open but won't continue round the circuit with it shut.

On this last rad the exciting pipe runs up a sharp 90 degree bend on its return up into a flat roof. Presumably it's air locked in the upwards straight?

What can I do to sort this?
I have no TRV's fitted on this system BTW.
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With all that draining I would have thought that you would have fitted some TRVs.

Balancing is fine. I even turned all the other manual valves off to just supply the cold rad and turned the pump up to full but no joy.
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All sorted. I had to shut off the rad valves and bleed the pipes either side, then run a lot of water out of the drain valve below the radiator. Not really what I wanted to do having just filled the system with Ferox F3 cleaner :(

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