What sludge is
Over time, the water inside a heating system corrodes steel radiators and pipes, producing a dark sludge. It's heavier than water, so it settles at the bottom of radiators, blocking the flow and leaving a cold area.
Fixing a sludged radiator
Options depend on how bad it is:
- Removing and flushing the individual radiator
- A chemical clean of the whole system
- A power flush for heavily sludged systems
- Replacing radiators that are badly corroded
- Fitting a magnetic filter and adding inhibitor afterwards
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Why it matters
Sludge doesn't just affect radiators. It can block the boiler's heat exchanger and damage the pump, leading to breakdowns. Many manufacturers recommend – or require – a clean system before fitting a new boiler.
