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three cold radiators

Postby berrikrown » Fri Nov 28, 2008 12:56 pm


i have 5 radiators downstairs but three of them will not heat up. we had someone come out who put cleaner into the system but this was a waste of time and money. as suggested by a friend i drained all the water out of them, increased the boiler pressure a little and then put the heating back on. as they filled back up they three broken ones did start to heat up a little so im presuming there is no blockage in the pipes. after bleeding some air out they did produce some heat that evening but since then everytime i put the heating on they still stay cold. i dont understand??

any advice would be greatly appreciated.
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Simply Build It

Postby plumbbob » Fri Nov 28, 2008 9:20 pm

The system needs balancing (see projects section) or the pipework is sludged up. Just 'cause the rad fills with warm water does not mean the pipes are clear. The rads need removing and flushing thoroughly and the pipework feed to them needs to be flushed too.

I assume the cleaner has been removed from the system?
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Postby Steve the gas » Sat Nov 29, 2008 6:46 am


Firstly, youve lost all that inhibitor.

Do you have TRVs on the rads if so, check the pins are free on the 2 rads by- unscrewing heads and pull/push pins no more than 2-3mm.

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Postby chris_linney » Sat Nov 29, 2008 8:53 am

firstly just because you get heat doesn't mean the pipe isn't nearly blocked , i have had many cases where 8mm tube has become blocked , or 10mm plastic tube becoming blocked , having said that i have come accross many that aren't, have you tried turning every radiator that heats off , all the upstairs and the remaining downstairs that heat , sometimes the pipework can get airlocked and you need to turn all the rest of the radiators off to force the air through the pipework otherwise it will just bypass thoase radiators, i'm assuming you have a combi boiler ,as you said pressure in the system, ok try the above if that doesnt work , the next step is to remove one of the inoperative radiators by turning the valve off at both ends if it doesnt apper to have a switch off it will be there under the white or grey cap , then that removed you should attach a hose pipe to one side of the pipework and then open the valve a little ata a time to see if you have flow then do the same at the other side , remember this water could be very black , make sure you have the heating off , you don't want to get scalded, AND REMEMBER PRESSURE IS DIFFERENT TO FLOW you can have a very high pressure with a poor flow , so don't assume its not blocked because it's got water dribbling out
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Postby berrikrown » Sun Nov 30, 2008 5:33 pm

Hi Everyone,

Thanks for the advice. I have completely no clue about plumbing but will try some of your suggestions starting with turning all the working ones off.

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