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Customers usually come to know of the term "Power Flush" when it's recommended to them because of experiencing one of the following common symptoms:

  • Brown/black contaminated water found in the system

  • Boiler making a kettling noise

  • Regular boiler breakdowns

  • Cold spots on radiators

  • Unexpectedly high gas bills

  • Radiators taking too long to heat up


As time goes by and the water in your radiator system gets repeatedly heated up and cooled down, rubbing against the internal parts of the pipes and radiators, it slowly forms rust and corrodes the metals to form a thick layer of sludge. This process is highly escalated when aerated water circulates in a system with inadequate amounts of a suitable corrosion inhibitor to prevent oxidation of the system metals. 





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(1) Sludge could build up inside the pipework; just like layers of fat settle around arteries, narrowing down the pipe diameter and restricting the flow. (2) Similarly, the sludge tends to settle down in low-flow areas of the circuit such as the bottom of radiators and block the flow of water through some of the pathways, leaving a cold spot.

When the pipework gets narrowed and the flow of water is reduced, it'll take longer for the radiators to heat up. When some of the pathways inside the radiators get blocked, and for instance the heating efficiency reduced by half, it will take twice as much time and gas to heat the room to a particularly set temperature. This will give you the toll on the gas bill.

Debris and corroded material, collectively referred to as sludge, can also get suspended in the system water and carried to the boiler with the flow. Boilers have a heat exchanger, where heat produced by burning gas is transferred to the central heating water medium. A heat exchanger consists of many layers of thin metal plates welded very close to each other to maximise the heat transfer surface area. However, these water passages are so narrow that larger sludge particles can get stuck in them, and in time there will be a build up even from the smaller particles that are in suspense. 


The partial blockage of water passages will reduce the heat transfer surface area and bring down the boiler efficiency, because the boiler will be producing heat that is not effectively transferred to the water. A more substantial blockage could cause kettling noise and overheating within the boiler. The boiler safety cut-out mechanisms would then be engaged to stop the heating and the boiler would continuously turn on and off. Persistent use of the boiler in this state could also cause damage to other components such as the expansion vessel. 



Whilst our machine utilises every effective way in breaking down sludge, and we allegedly spend the longest time during the flush, experience shows that in highly contaminated systems power flushing is only able to scrape off as many layers of sludge as possible. But there will still remain more layers of sludge on the interior of pipes and radiators, which may in time come loose into circulation. That's why we recommend the installation of a magnetic filter, where this is not present in the system.

It is a good idea to install the magnetic filter whilst performing the power flush, as it will save the engineer time to drain the system and top it up with new corrosion inhibitor. As a result, these savings can be passed on to you with regards to the cost. So, the addition of a magnetic filter to your system on the day will be at a fraction of its normal cost. If you're interested, please arrange this with the engineer prior to the power flush date.

No Magnetic Filter.jpg


With Magnetic Filter.jpg


For your information, it is also a requirement of the Part L of the Building Regulations to upgrade all radiator valves to Thermostatic Radiator Valves (TRVs) whilst a central heating system has been drained, in order to preserve the use of energy. This will both improve the temperature control in each room to stay at comfortable levels and will save on your energy bills by preventing overuse. Again, integrating this work alongside your power flush will add to your savings on the labour charges.

For more information or to book, please visit our Prices or Book Online page.


Blocked Heat Exchanger



Clean Heat Exchanger


Power flush is the process of physically agitating and chemically breaking down the accumulated sludge in the system using a specialised power flush machine to restore maximum heating efficiency to the system and prevent damage to the boiler.


Whilst conventional power flush machines are being used by other operators, London Heating Expert has invested in the development and use of its own patent-pending power flush machine. And what's more is that no other operator spends as much time on your system. Some people spend no more than a couple of hours for what they call a power flush. However, effective breakdown of sludge takes time and individual radiators must be given a dedicated treatment, each. That's why London Heating Expert usually spends no less than 6-12 hours on a typical power flush job. When comparing our service with others, it's good to know how long they will be spending on the job!

Custom-Built Power Flush Machine
Custom-Built Power Flush Machine

Our research and engineering has so far produced two working prototypes with the third under way! We are constantly building on our specialist knowledge of power flushing and making innovatory improvements to our equipment.


The current working prototype, pictured above, gives the following operational advantages:


  1. High Pressure in the system. Most conventional power flush machines are unpressurised open vented machines (like our first prototype); but this device uses a sealed system approach and could attack the system build-ups at higher pressures. Increased pressure means multiplied collisions between chemical particles and sludge particles per second. What's also unique about this device, is that it incorporates its own expansion vessel, so old open-vented systems can also be flushed at higher pressures whilst heated.

  2. High temperature. The sealed-system design of our power flush machine allows it to be used alongside an operating boiler. The heat from the boiler is used to raise system water temperature during the flush. Power flushing at higher temperatures maximises the effect of the treatment with chemicals.

  3. High water flow. Conventional power flush machines use a water pump with a maximum delivery of about 5,000 litres per hour. We've used an industrial pump with a flow rate of about 20,000 l/h, i.e. 4 times as fast a flow.

  4. Reverse Flow. This is the minimal requirement for a power flush device, to be able to reverse water flow direction in order to break down system build-ups more effectively. Reversing the flow creates a hammering effect to dislodge stubborn and hardened sludge as well as particles which would be otherwise entrapped in a unidirectional flow.

  5. Use of flushing chemicals. These are industry standard chemicals which breakdown sludge and corroded metal bits into tiny particles which can then be easily flushed out of the system. We use well known brands such as Sentinel, Fernox, Adey or Corgi, etc. to suit different system conditions.

For more information or to book, please visit our Prices or Book Online page.



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