Why are my radiators cold?
Where the radiator is cold tells you the cause. Cold at the bottom but warm at the top usually means sludge. Cold at the top means trapped air. Some radiators hot and others cold usually means the system needs balancing or has sludge in it. If every radiator is cold, the problem is usually the boiler, pump, thermostat or a valve. Sludge is the one cause that gets worse over time, and a powerflush clears it.
Cold at the bottom, warm at the top
This is the classic sign of sludge. Corrosion inside the system makes black magnetite sludge, which settles along the bottom of the radiator and blocks the hot water. Bleeding won’t help. More on radiators cold at the bottom.
Cold at the top, warm at the bottom
Air has collected in the top of the radiator. It usually needs bleeding. If it keeps coming back every few weeks, something is letting air in or making gas inside the system, which is worth having checked. More on radiators cold at the top.
Some radiators hot, others cold
If the radiators furthest from the boiler, or the ones upstairs, are the cold ones, the system may need balancing, or sludge may be slowing the flow so the hot water never gets that far. Radiators cold upstairs?
Every radiator cold
If nothing is warming up, look at the boiler first: is it on, is there a fault code, is the pressure right, and is the thermostat or timer asking for heat? A failed pump or motorised valve can also stop the heating while the hot water still works. These need a heating engineer.
Still cold after bleeding?
That points strongly to sludge rather than air. Read our guide to radiators still cold after bleeding.
In Kent?
Kent Powerflush, Gas Safe 660156, covers Faversham, Canterbury, Whitstable, Herne Bay, Thanet, Sandwich, Deal, Dover, Folkestone, Ashford and Sittingbourne, up to Maidstone, Sevenoaks and Gillingham, and Rye.
Local pages: powerflush in Canterbury, powerflush in Margate, powerflush in Sandwich, or see all the areas we cover.
Questions people ask
Why is only one radiator cold?
Usually a valve that is closed or stuck, trapped air, or sludge that has gathered in that one radiator. If the cold patch is along the bottom, it is sludge.
Why are my radiators cold but the hot water is fine?
The boiler is working, so the fault is on the heating side: often the motorised valve, the pump, or the thermostat or timer. A heating engineer can test each part.
Can sludge make all my radiators cold?
It can make them all cooler, especially at the bottom, and slow the whole system down. If several radiators are cold at the bottom, a powerflush cleans the whole system.
Do you fix cold radiators in Kent?
Yes. Kent Powerflush covers East Kent, from Faversham and Canterbury to Thanet, Deal, Dover, Folkestone and Ashford.
Related guides
Hot radiators across East Kent
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