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Central Heating

One radiator not getting hot, how can i fix it?


One radiator in my house refuses to get more than luke-warm (and when it does get luke-warm it is warmer at the top than at the bottom -- the opposite of when a radiator needs bleeding).

The pipe which leads to the radiator gets very hot, so I would presume it's some kind of problem with the water entering/exiting this particular radiator. Could it be that the valves need replacing?

I have tried to follow the Youtube advice here but to no avail (the bit about the pin which you can push down in the TRV didn't seem to correspond to what was on my radiator however -- my radiator didn't even seem to have a proper TRV like the one in the video, just a knob indicating "SHUT" with a clockwise-pointing arrow).

Does anyone have any thoughts as to whether this is something I could repair myself or will I need professional help?

all the best

1 Answer from a MyBuilder Heating Engineer

Best Answer

It's quite likely that the radiator is blocked with sludge, as you describe the top being warmer than the bottom.
Sometimes the sludge can block the radiator valve ports, so in time you may want to change these, along with the radiator itself.
There are several generic chemical cleansers that you could introduce into the system which may well disperse the build up of sludge, but in the meantime try this :

Turn heating on / hot water off, (assuming it's not a combination boiler, where the water will be on demand only).

Turn the room thermostat up to maximum, turn the boiler thermostat up to maximum.

Wait for the radiators to become piping hot.

As soon as each radiator becomes red hot, shut one of it,s valves down fully.

You should end up with all the radiators hot, with their individual valves turned off leaving the pump to try and force the water through the boiler and the effected cold radiator.

This may well alone get the radiator working, though I would suspect that you will require some sort of chemical flushing of the system.

Let me know how you get on, and I caould always talk you through the flushing and radiator balancing process.

Happy New Year

Adrian Hagger

southsea plumbing and heating


Answered 31st Dec 2012

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