Two cold radiators downstairs

17 Nov 2007
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United Kingdom
I have two downstairs radiators not working and completely cold. The rest of the system is fine. The heating had been switched off all summer after working perfectly last winter.
Both radiators are fed by a pair if pipes from upstairs, have drain cocks, are full of water and have been bled.
Both had new TRVs fitted last year and the pins are free to move.
All radiators were flushed out with a pressure washer last year, and new TRVs fitted throughout.

I assumed there was an airlock in an upstairs pipe so drained the system.
However the expansion tank in the loft, would not empty when I drained the system from the downstairs faulty radiator. I took the opportunity to empty and clean the tank by hand.
I then tried forcing mains water into the tank's outlet pipe but it didn't seem to go anywhere except back into the tank.

I then drained the system from the downstairs cold radiator drain cock. Because the expansion tank was not emptying I refilled the system by forcing mains water back up the radiator drain cock.
This eventually fed some water back into the expansion tank via its outlet pipe so I assume it isn't blocked.
The two radiators are still not working.

Can anyone please suggest how to cure the two cold radiators, and clear a possibly blocked outlet pipe on the expansion tank?
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have ya tried turning the upstairs rads off to force any airlocks out the drops?

ya said the tank wouldn't empty wen ya drained the system, sounds like ya cold feed is blocked. if it is it would affect the circulation, the pump requires a head of water to work affectively. id make sure it int blocked before doin owt else!
Thanks, I tried turning all the rads off except the cold ones, but it didn't help.

I eventually got the feed tank to empty by draining the system and refilling it from the bottom drain cock several times. I think this might have stirred up some sludge.

The cold rads are now slightly warm so I'm going to turn all the others off again and see what happens.

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