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AnswerWhy is my radiator cold at the bottom?
A radiator that's warm at the top but cold at the bottom usually has a sludge (magnetite) build-up restricting flow — it needs flushing, and a magnetic filter fitted to prevent it recurring.
In more detail
This is different from being cold at the top, which is trapped air you can bleed out.
2026 figures · BTU uses standard UK heat-loss methodology; running costs use the Ofgem price cap · always confirm with a professional.