Power flush service

Clearing sludge and debris from your heating circuit so radiators and boiler can do their job.

Gas Safe registered (554328) Worcester Bosch accredited Free, no-obligation quotes

What we offer

A power flush pushes water and cleaning chemicals through your heating system at a high flow rate to lift out sludge, rust and scale that have settled in the radiators and pipework. It is the job we carry out when a system is clearly dirty, before a new boiler goes onto old pipework, or when radiators stay stubbornly cold at the bottom however long the heating runs.

This page covers our power flushing service and what happens on the day. If you want the background first, our advice article explains how power flushing works and our cost guide covers what affects the price. John The Plumb is Gas Safe registered (554328) and fits a magnetic system filter as standard, and every flush is quoted at a fixed price in writing.

Cold spots and sludge cleared
Every radiator flushed in turn
Corrosion inhibitor added afterwards
Magnetic system filter fitted as standard

Get a free quote 07891 410 960

Signs your system may need a power flush

The classic sign is a radiator that is hot at the top and cold across the bottom, which usually means sludge has settled inside it. Other clues include radiators that take a long time to warm up, dark or black water when a radiator is bled, a boiler that kettles or bangs, and a pump that sounds strained. These symptoms can have other causes, so we test the system water and look at how the radiators behave before recommending a flush. If a simpler clean will do the job, we will say so.

What happens on the day

The flushing machine is connected into the circuit, usually at the pump or at a radiator. Cleaning chemical is circulated, and each radiator is isolated and flushed in turn so the dirty water is driven out rather than simply moved around. The flow direction can be reversed to dislodge stubborn deposits, and radiators may be agitated to help loosen sludge. The dirty water is dumped to drain and replaced with clean water until it runs clear. Expect the heating and hot water to be off while the work is under way.

Protecting the system afterwards

Cleaning is only half the job. Once the water runs clear, a corrosion inhibitor is added to slow the formation of new sludge. We fit a magnetic system filter as standard, which catches iron particles as they circulate so they collect in a chamber that can be emptied, rather than settling in the radiators or the boiler heat exchanger. The radiators are then bled and the system checked so you can see the improvement for yourself at handover.

Power flushing before a new boiler

Modern boilers have narrow waterways that do not cope well with debris from an old system. Cleaning the circuit is therefore part of the conversation whenever we replace a boiler, and boiler manufacturers expect the system to be properly cleaned when a new appliance is fitted. Whether that means a full power flush or a lighter chemical clean depends on the condition of the water and the pipework. If you are planning a boiler replacement, the survey covers both, so the quote shows the cleaning method included.

When a power flush is not the right answer

A flush cannot fix a failed pump, a seized valve or a radiator that is corroding through. On very old or fragile pipework, a gentler method may be the safer choice, and a radiator with heavy internal corrosion is sometimes better replaced than cleaned. Microbore pipework and some older layouts also need care. We look at all of this before quoting, so you get the method that suits your system rather than a standard package.

FAQs

Frequently asked questions

How long does a power flush take?+

Most take a working day, depending on the number of radiators and how dirty the system is. Larger homes or heavily sludged systems can take longer.

Do I need a power flush with a new boiler?+

The system needs to be properly cleaned when a new boiler is fitted. A power flush is one way of doing that; on cleaner systems a chemical clean may be enough. We check the water during the survey and include the right method in the quote.

Power flush or chemical clean?+

A power flush uses a pump to drive cleaning chemical through each radiator at high flow, while a chemical clean relies on the system's own circulation. Heavier sludge usually calls for a power flush. Our comparison page sets out the differences in more detail.

Related services

Power flushing explained What affects power flush cost Power flush vs chemical clean Central heating installation Boiler replacement Radiator replacement

Get your heating flowing again

Book a free survey and we will check whether a power flush is the right fix for your system.

Get a free quote 07891 410 960