Why should I get the water in my central heating system cleaned?

If sludge is allowed to build up, it can result in blocked pipes, inefficient radiators and damaged parts in the boiler.


The heat exchanger in a boiler consists of many narrow pipes which the water passes through to heat up.  If the narrow pipes become restricted or blocked, the boiler will shut down to prevent it from overheating and getting even more damaged.  If the boiler breaks down because of sludge in the system, the repair work is not covered by the boiler warranty and could lead to expensive repair bills.


Sludge can cause:


  • Damage to the boiler
  • Damage to the boiler pump
  • Damage to radiators, including leaks
  • Damage to radiator valves
  • Blocked pipework, including on the heat exchanger
  • Higher energy bills

What is central heating sludge?

Sludge, or magnetite, to give it its proper name, is a black substance in the central heating pipes made up of dissolved and rusted metal.

How do I know if I've got sludge in my central heating system?

Read on to find out what the common signs of sludge in your central heating system are.

Related FAQs

Why should I get the water in my central heating system cleaned?

If your boiler breaks down due to sludge in the system, the repair work is not covered under your warranty and can lead to expensive repair bills as a result.

Why should I have a filter fitted?

Many boiler breakdowns occur due to sludge in the heating system. A magnetic filter is an effective way of preventing this sludge from accumulating, and may prevent costly breakdowns at a later stage.

Why are my radiators cold?

If you notice that your radiators are cold to the touch, you may have air or sludge trapped inside the system. These can be simple to resolve, but if you’re concerned, contact a heating engineer to help.

How do I know if I've got sludge in my central heating system?

Issues with your radiator temperature, leaks from your boiler, and unusual sounds from within your system are all indicators that there is a buildup of sludge.

Does my boiler filter need cleaning?

Your boiler filter should always be cleaned as part of your boiler’s annual service.

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