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Central heating care

Central heating
system flush.

A system flush cleans the water side of your central heating. The method, from draining and refilling to a chemical flush or power flush, is chosen to suit the system. We assess your information and advise what is suitable.

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Magnetic central heating filter fitted on a heating pipe between two isolation valves

What system flushing means

A central heating system flush cleans the water side of the heating circuit: removing sludge, rust and debris and replacing the dirty system water with clean water that is then treated with inhibitor. “Flushing” is a general term. The method used can range from draining and refilling to a chemical flush or a machine power flush, and it is chosen to suit the system.

No method guarantees that circulation, sludge or heating-performance problems will be resolved. Radiators and boilers can misbehave for reasons that cleaning does not fix.

Common flushing methods

MethodIn brief
Draining and refillingReplaces system water. May be part of other work. Does not by itself remove settled sludge.
Chemical flushA cleaner is circulated at normal system flow, then the system is drained, rinsed and treated. See chemical flush.
Power flushA pump unit circulates water at high flow, often in both directions, usually with chemicals. A more intensive method. See power flushing.
Individual radiator cleaningA radiator is removed and cleaned separately, for example where one radiator stays cold.

Chemical flushing and power flushing are different methods, not interchangeable ones. Which is appropriate depends on the system.

How the appropriate method is chosen

We look at:

  • The symptoms and how long they have been present.
  • The boiler type and any manufacturer cleaning requirements.
  • Pipework material and layout, including microbore sections, and the number and type of radiators.
  • Previous cleaning, inhibitor or filter fitted.
  • Known leaks, blockages or system faults.
  • Access to radiators, valves, drain points and the boiler.

Sometimes the answer is that a flush is not the right step, or that a repair should come first.

Why customers ask about a flush

Typical reasons include:

  • Radiators cold at the bottom or slow to heat.
  • Dirty or black water when bleeding a radiator.
  • A noisy boiler or pump.
  • Fitting a new boiler to an older system.
  • General system maintenance.

If you are having a new boiler fitted, see our online boiler price; cleaning requirements depend on the boiler manufacturer and the installation.

System condition, access and suitability

Suitability depends on the condition of the system as well as the symptoms. Older steel radiators and pipework, existing leaks, restricted pipework or inaccessible valves can all change what is sensible. Access matters too: we need to reach the boiler, the radiators and suitable points to isolate and drain the system. Tell us about parking, keys and access restrictions when you request your quotation.

What happens after you request a quotation

  1. You send the details through the quotation request, ideally with photographs or a short video of the boiler and radiators.
  2. We review the information and advise whether a quotation can be provided remotely or an on-site survey is required.
  3. If an on-site survey carries a charge, we confirm the cost and you agree it before booking.
  4. You receive a written quotation that names the method, what is included and the price, before any work is agreed.

Requesting a quotation online is free. We review the information you send and advise whether a quotation can be provided remotely or an on-site survey is required. Any applicable on-site survey charge is confirmed and agreed before you book.

Frequently asked questions

Does every heating system need flushing?

No. A flush is worth considering where contamination is affecting a system, or as part of fitting a new boiler where the manufacturer requires the system to be cleaned. A cold radiator or boiler fault does not by itself show that a flush is needed.

Can a flush cause problems in an older system?

Cleaning can reveal existing weaknesses, such as pinhole leaks in corroded pipework or radiators. We discuss the system’s condition and this possibility before any work is agreed, and a different method may be advised for fragile systems.

How is the flushing method chosen?

After we review the symptoms, boiler, pipework, radiators, previous treatment and access. We then advise whether a chemical flush, a power flush or another approach is appropriate.

Is requesting a quotation free?

Yes. We review the information you send and advise whether a quotation can be provided remotely or an on-site survey is required. Any applicable on-site survey charge is confirmed and agreed before you book.

Related

More about cleaning and protecting a heating system:

Chemical flushCentral heating system flushPower flushingRequest a quotationMagnetic filtersPower flush cost in London

Areas we cover

We assess and quote for heating-system cleaning across these East and North London areas. Coverage depends on the full postcode, which we confirm when you request a quotation. The postcode districts shown on each area page are a guide only.

Local power flushing pages: Leyton E10, Barking Ig11, Beckton E6, Bethnal Green E2, Bow E3, Buckhurst Hill Ig9, Canary Wharf E14, Canning Town E16, Chigwell Ig7, Chingford E4, Clayhalll Ig5, East Ham E6, Edmonton N9, Forest Gate E7, Gants Hill Ig2, Clapton E5, Dalston E8, Victoria Park E9, Ilford Ig1, Leytonstone E11, Manor Park E12, Plaistow E13, Redbridge Ig4, Shoreditch E2, South Woodford E18, Stratford E15, Tottenham N17, Walthamstow E17, Wanstead E11, Whitechapel E1, Woodford Green Ig8.