Put your hand on the radiator. Warm across the top, cold along the bottom band. That pattern is one of the most common calls we get as a local heating engineer in Bridgend, and it almost never means the radiator is dead.
What is in there
Steel radiators corrode slowly from the inside. The result is magnetite, a black iron oxide sludge, that circulates around the system until something catches it. Without a magnetic filter, nothing does. It sinks to the lowest point, which is the bottom of the radiator, and blocks the flow there.
Heat rises and dirt sinks. That is why the cold patch tells you the fault:
- Cold at the top: air. Bleed it.
- Cold along the bottom: sludge. Bleeding will not touch it.
- Cool all over: that radiator is getting less flow than the ones nearer the boiler, which is usually balancing.
One radiator or several?
If it is one radiator, it can often be taken off the wall, flushed through outside and refitted. That is a small job.
If several radiators are doing it, the sludge is right round the system, including in the boiler’s heat exchanger. That is where a powerflush earns its money: the whole system flushed with the machine and the right chemicals, then a magnetic filter fitted so the sludge is caught instead of settling again.
Signs it is getting serious
- Black water when you bleed a radiator
- The boiler bangs or kettles when it heats up
- Radiators that used to be fine are going cold one by one
Any of those means the dirt is shortening the life of the boiler, not just making a room chilly.
What it costs
A single radiator flush or a full powerflush is priced before we start, once we know how many radiators and how bad it is. If one radiator coming off is enough, we will tell you that rather than sell you a full flush. Send us the job.