Why is my radiator cold at the bottom?

Put your hand on the radiator. Warm at the top, cold at the bottom? That's not air — it's sludge. Air rises, so a radiator with trapped air is cold at the top and fixed with a simple bleed. Cold at the bottom means dense, heavy sludge has settled where the water should flow.

The thermal image above shows exactly what that looks like: the bright areas are hot water flowing properly, the dark patch is where sludge is blocking circulation. This is how we diagnose radiator problems — no guesswork, no unnecessary work.

Sludge is magnetite: rust and debris from inside your system. One sludged radiator usually means the whole system is affected, and it's costing you money — a sludged system forces your boiler to work harder for the same warmth.

The fix is a powerflush: we circulate cleaning chemicals through the system at high velocity, dislodge the sludge, flush it out, and add inhibitor to slow future corrosion. A magnetic filter fitted afterwards catches whatever forms next before it reaches your boiler.

If your radiators need bleeding every few weeks, take ages to warm up, or have permanent cold patches, get in touch — we'll take a look with the thermal camera and tell you exactly what's going on.