2 radiator cold at bottom

Hi we have a 2 radiators cold at bottom 

One is a double radiator.

System is just 6 years old.

Bar pressure is at 1.5 not on and 2 when on

Do we need to have the hole house System cleaned or just the 2 effetected radiators??


  • FreeBear
    FreeBear Posts: 14,269
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    Assuming the entire system is just 6 years old, it won't need flushing unless you've been running it without any corrosion inhibitor for all that time.
    At most, I would suggest a chemical clean, fit a magnetic filter, and then have all the radiators balanced.
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  • ThisIsWeird
    ThisIsWeird Posts: 4,458
    First Anniversary First Post Name Dropper
    How DIYish are you?
    Cold bottoms are a classic symptom of a build up of sludge in a CH system. This suggests that it either wasn't cleaned properly when a boiler was replaced on an older system, or - given yours is only 6 years old - one that hasn't had corrosion inhibitor added when new, or if the system had subsequently been drained and refilled.
    Was a magnetic filter added - this should be on the return pipe before the boiler?
    First thing is to determine the cause of your cold botts. It could also be caused by just an inadequate flow through these rads. So ..
    1) how hot do the tops become? As hot as other rads? And as quickly?
    2) have a good feel of the cold areas. How 'defined' are they? Is the middle-bottom pretty much stone cold? How wide and high is the cold area?
    3) when did this begin happening? Any idea if it's gradual or quite sudden?
    4) which rads? Where are they located, storey, etc. Are they always on, or used only occasionally? And only two cold rads in how many?

    If it looks like sludge, then it would be best to first remove these rads and flush them through outside. That should ensure the majority of the sludge is successfully removed, and also prevent it from going into the rest of the system. You can DIY this quite easily, but I'm not sure a plumber would bother. They would usually fit a large filter to the pipework, and pump round some chemicals whilst agitating each rad in turn to shift any collected sludge. 
    A small magnetic filter should be fitted afterwards in order to keep collecting any remaining sludge.
  • Veteransaver
    Veteransaver Posts: 342
    Name Dropper First Post
    Are the tops of the rads getting hot? It could just be a lack of flow to the rads, you could open the lock shield up fully on one side, or if there's a thermostatic valve on the other side that may have become "sticky".
    Is the flow pipe on one side getting hot?
    Are the 2 rads among the furthest ones from the boiler? It could just need the central heating pump speed increased.

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