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Trusted by over 500,000 customers for 20+ years
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01480 775454
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Trusted by over 500,000 customers for 20+ years
Written by
Jenna Culy
on 03 Jun 2026
and updated on
03 Jun 2026
Categorised in
Tips and Advice
A power flush is a procedure that is designed to clean your central heating system by removing any sludge, rust or debris that may have built up over time.
Before a power flush begins, a heating engineer should first assess the condition of your radiators and pipework to ensure the system is suitable for the process. Older or weakened radiators may already have areas of corrosion, and the increased flow during a power flush can sometimes expose weak points and cause leaks.
Many boiler and central heating system problems are caused by sludge buildup in the system, so power flushing can help prevent boiler breakdowns and related maintenance costs.
WARNING: You should never attempt to power flush your system yourself, as this could cause considerable damage to your central heating apparatus.
Your central heating system may require a power flush if you are experiencing some or all of the following problems:
It is also recommended that you power flush your system before you have a new boiler fitted to make sure that all debris is removed from the system. This is especially important when replacing a boiler, as existing sludge can affect the performance and efficiency of the new appliance and may lead to future issues if left untreated.
WARNING: Many boilers’ warranties state that your policy will be void unless the system is power flushed before the boiler is installed, as any lingering rust or particles can damage the boiler and block the filters.
Power flushing is a fairly simple procedure:
Your heating engineer will attach a high flow, low pressure pump to your central heating system.
A cleaning solution is then pushed through the system to flush out any rust, sludge, or debris. The solution usually contains a light acid-based chemical as well as a descaler which can help to remove any limescale buildup.
After the process is complete, your central heating system will be flushed with clean water. The engineer will test a sample of water to make sure that there is no acid left in the system.
A rust inhibitor should then be pumped into the central heating system to help prevent further build-up. Some companies charge extra for this, so check if it is included in your quote before you book the service.
IMPORTANT: Power flushing may not be suitable for microbore or open-vented central heating systems, as the higher flow rate can sometimes cause damage or dislodge debris too aggressively. In these cases, a gentler chemical flush or mains flush may be more appropriate for removing sludge and debris.
This will depend on the size of your central heating system and the amount of work required. Most companies quote a starting price of £350, but it is not unheard-of power flushing to cost more than £1,200. You should be wary of insurance companies that offer a power flush service attached to an insurance policy, as they may charge a lot more for the service than an engineer would.
On average, a routine power flushing service takes between 4 and 6 hours, however, this can differ depending on the size of your central heating system and the amount of rust or sludge present.
You should always use a qualified heating engineer or heating company to carry out a power flush. When choosing an engineer, check that they have insurance that will cover any damages that may occur if any problems arise during the service.
You can find further information on power flushing at The Power Flush Association website or ask a qualified engineer during your annual boiler service.
If you're experiencing problems with your central heating system, the best thing to do is book a boiler service with a qualified engineer. Simply click below or contact our team on 01480 775454 to get a free, instant service quote from qualified engineers in your local area now.
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