Cold radiators

[nothernexposure]

Hi, I've noticed a few of my radiators are struggling to get warm. They're almost cold at the bottom with the top 10 - 20 cms being luke warm. With the COL the thermostat isnt as high has previously but its high enough for them to get warm! Any ideas how I solve this? Would getting the system flushed out help? Really dont want to spend the winter freezing 🥶 thanks

You just need to bleed the radiator (let the air out with a special key).

Try running the heating with only the weak radiators for 20-30 minutes. Turn off all working radiators. Then once they are red hot turn all back on and see if the situation has improved.

more advice here if needed.

Thanks @KateyCuckoo but that makes no difference. They're bled a couple of times a year and as I understand it you bleed them when they're hot at the bottom and cold at the top.

Ah OK.

Maybe try the other suggestion then???

For the last two winters we've had problems with two large downstairs rads which are freezing cold while all the upstairs ones are boiling hot. Plumber came out year before last and spent two hours turning rads on and off with no success. Scratched his head and left. It pisses me off though so I'll have to do something about it this year.

See if anything here helps:
https://idealheating.com/tips-and-advice/radiator-cold-at-the-bottom-possible-causes-and-solutions#:~:text=If%20your%20radiators%20are%20cold,it%20cold%20at%20the%20bottom.

If it's sludge then you could try flushing your heating system. Are you in a hard water area? That also doesn't help, you could have scale as well as sludge.

Have you got thermostatic valves on each rad and if so are they fully open and do you operate them periodically to prevent them sticking?

This worked with mine. I was amazed how quickly it sorted it out.

Chemical flush for the sludge.
Leave the cleaning fluid in for a few days then drain the system ( this is for a combi boiler NOT a system boiler which is trickier to drain down as you would have to plug the cold water feed tank) refill with fresh water, drain again then fill and add inhibitor.

@filka thanks for the link, looks like crud in the radiators is the problem so worth getting it flushed to see if that helps. I'll also give @4naansjeremy trick a go to see if that helps. Have got thermostatic valves on most of the rads but rarely change the settings so that won't help. I feel your pain @TeenagersAngst as my plumber has ghosted me this winter....

The plumber we used did as @4naansjeremy said - and then he did some kind of rebalancing thing

I've tried your suggestion @4naansjeremy and my cold radiators definitely got much hotter, thank you! I've turned the other rads on full blast so will see if they all remain hotter. And I'll also get someone to flush the system ad I cant remember the last time it was done