Why is my radiator cold at the bottom?

Warm at the top, cold along the bottom? That's not air — it's sludge. Here's what's really going on.

Cold radiators explained No gas needed Free advice

It's one of the most common heating gripes: the top of the radiator gets nice and warm, but run your hand along the bottom and it's stone cold. If that sounds familiar, the culprit is almost always sludge — a thick, gritty build-up of rust and muck that settles in the bottom of the radiator over the years and stops the hot water getting through.

Remember when your home actually felt warm and cosy? Sludge is usually why it doesn't any more.

Cold at the bottom vs cold at the top

This bit matters, because the fix is different:

  • Cold at the bottom, warm at the top — that's sludge sitting in the radiator. Bleeding won't help. It needs flushing out.
  • Cold at the top, warm at the bottom — that's trapped air, and a quick bleed usually sorts it.

So if you've been bleeding a radiator that's cold along the bottom and wondering why nothing changes, that's why.

What actually fixes it

To get the heat back you have to clear the sludge out of the system, and that's what a power flush does. Declan Gent flushes clean water and a cleaner through the system under pressure, shifts the muck out, and adds a protector to keep it clean — bringing a tired old system genuinely back to life for a fraction of the cost of a new boiler.

Dec covers Exeter and Devon, works on the plumbing (wet) side of heating, and will tell you honestly whether a flush will help before you spend anything.

Free quote, no obligation

Get your radiators warm again

Call or text Dec on 07493 772609, or send a few details and he’ll get back to you.