Cold Radiators, 10mm microbore...

18 Oct 2023
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United Kingdom
Hi All,

The hours has a fairly modern (last 10 years) heating system, a number of radiators upstairs are cold (they were not great last year, but the year before they were fine). I have taken them off the wall and flushed them, but there appears to be a blockage somewhere. I believe there was not enough inhibitor in the system (we bought the house 3 years ago). I have tried flushing with sentinel x400, but as there is a blockage it didn't touch it, from what I understand it really needs flow to work effectively.

I have managed to find the manifold for these radiators. There are two manifolds, one connecting the flow and the other the return to the 10mm microbore. In the picture below the top manifold is the flow and the 10mm pipes connected to this are warm, however the bottom manifold is the return, and these pipes are cold.

I'm fairly handy around the house, but typically shy away from plumbing. Do you think the manifold is the most likely place where the blockage will be? Would you suggest draining down the system and disconnecting them and giving them a good clean out / replacing? If I do attempt to disconnect is it as simple as unscrewing the grey collar that connects to the 22mm flow / return and pulling the manifold off?

Many Thanks


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How many radiators upstairs are cold ,and how many upstairs rads do you have in total ?
If you do decide to drain the system ,and check out the manifolds cleanliness, the connections are all demountable .
There are 12 rads upstairs. All 6 that I believe are fed by this manifold are cold. I haven’t found the manifold for the other 6 rads, but they are all working fine.
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Installed in the last 10 years, not impossible, but unlikely a blockage. Have you had any work done which could have affected the balancing, including removing a radiator?

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