Sludge In Radiators

4 Oct 2007
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United Kingdom
Hi All,

Ive been trying to tackle a problem with three radiators I have downstairs that appear to have significant sludge buildup. Hot on top and cold across most of the radiator/s.

I intitially got a powerflush done by a local plumber/Gas engineer but this failed to shift any sludge. We then decided to remove the said radiators and flush with a hose pipe and this seemed to flush quite alot of sludge out of all three raditors black oil in consistency.

Upon reinstating the radiators they still fail to warm up sufficiently, now my question is would it be worth trying to flush them again or just bite the bullet and buy new ones. There fairly large double panel 600x1400 so would be quite expensive. Is it quite common for a radiator to be that sludged that even flushing fails to shift the sludge?

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balance all the radiators

Did you use a cleaning chemical before flushing?
I intitially got a powerflush done by a local plumber/Gas engineer but this failed to shift any sludge.

I hope you didn't pay them for it then... If there's enough flow there for the rads to get warm on top, there's enough for a powerflush to clear the muck out if it's done correctly. You won't clear a total blockage with a powerflush but rads with cold spots can be done, might take some time but should always get there in the end
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Do you have an air seperator fitted as these do block up and restrict the flow around the circuit considerably
It is fair to say that powerflushing alone will not remove solidified sludge. I would remove the rads and tap them on the wall side using a rubber mallet while flushing with garden hose in a final attempt to dislodge solid material.
That has worked a number of times for me although it is time consuming.
Balance the rads after that and see how you go. Total cost......your time.
Adding a bottle of X400 for a few weeks really does work in loosening sediment so it can be washed round and flushed or drained out.

I am not a pro but found it very satisfying, after a plain-water flush and fitting a Magnaclean, to see how much extra black was trapped by putting in the chemical cleaner. It will cost you about £15.

Some of the sediment will be hardened limescale, coloured black by being mixed with magnetite. This is very hard to dislodge without mechanical poking or a stronger cleaner.
Thanks for all the responses still a bit confused by it all have taken all radiators outside and given them a heavy spanking with a rubber mallet previously. I dont think its aflow issue as three other rads downstairs get hotter than hell as do the upstairs rads.
ive turned all the rads off apart from one of the affected and its still doing the same surely balancing aint going to fix it?
sorry for resurrecting this post but have been busy with other things, just a recap on what ive done so far and a little history

I moved into the house in august and he system is a ariston a27 combi, shortly after moving in noticed the bottom half of three of the radiators were cold but top half boiling hot. I also had the filling loop and a gasket replaced as water was leaking very slightly needing the pressure to be topped every week or so, meaning there was prob no inhibitor.

1.) Got a powerflush done using x800 by local plumber
2.) Asked him to remove one of the troubled radiator to see if there was any black sludge in system.
3.) Found sludge in radiator so took hose pipe and large mallet and hit radiator for several minutes until water ran clear.
4.) repated two three other rads that seemed to be a problem
5.) hesating back on and have spent a few weeks trying to balance the system but three rads down stairs still cool on the bottom.

Another gas engineer has suggested replacing them. Any thoughts from the experts.


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