Why a radiator
won't heat up

A cold radiator in a warm house almost always has a simple explanation. What matters is exactly where it's cold.

Warm at the bottom, cold on top

It's the most common case and it means air trapped in the radiator. It's fixed with a bleed, through the valve at the end. Simple, but it has to be done carefully, with a cloth at hand.

Cold all over

First check the radiator valves, that they're open. If they are and it's still cold, it's usually sludge blocking the flow, especially in older radiators.

A cold radiator isn't a whim. It's telling you the water isn't getting where it should.

When a flush is needed

If several radiators are cold in the lower part, the system has filled with deposits and needs a flush. After it, the heat spreads evenly through the house again.