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Power Flush your Central Heating System

Power Flush your Central Heating System

Power Flush your Central Heating System

The Problem

As you continuously make use of your central heating system, oxide sludge and calcium may begin to accumulate in the system. The build up of sludge or calcium in your heating system is mostly indicative of an underlying problem that allows air to get into the central heating system, corroding the radiators and heat exchangers in the process.

The rust and debris left behind by this corrosion in the bottom of the radiators quickly become oxide sludge due to further reactions with air. Oxide sludge ultimately causes a blockage of the waterways in the pipe work, radiators and heat exchangers.

A blocked pipe, radiator or water work makes your central heating system much less efficient than it should be. Over time, it causes severe damage to your heating control, pipes and valves. This damage is not always easily fixed, condemning your boiler to the list of items to be replaced in your home.

Without addressing the root cause of the boiler change, though, you might be needing another boiler soon enough. From the new boiler to the replaced heating controls, everything could be condemned in no time due to the continued presence of oxide sludge.

Thus, even when you have to change your boiler and heating controls due to the damage, it is important that you power flush your heating system to ensure that the problem doesn’t simply resurface. Power flushing your central heating system cleanses it, making it more efficient and saving you money on heating bills.

Keeping your radiators and entire central heating system functioning properly is important if you are to keep warm through the winter. There are several indicative symptoms that alerts you to the need of a power flush. Identifying these symptoms on time will save you from having to even replace your boiler due to the presence of sludge. First, though, you want find out what is involved in a power flush.

Power Flushing – What is it?

A power flush is a process used in cleaning out a central heating system. It combines the use of large volumes of high powered water and cleaning agents which is circulated around the heating system, to remove debris and rust from your system.

If your radiator begins to feel cold at the bottom and warm at the top, or you have cold spots in your radiators, it is usually an indicator of the presence of a sludge in your radiators. This temperature change can also be an indicator of a failure of one of the radiators in your system. Either way, a power flush would help revive your system.

When sludge builds up in the feed and expansion tank, or the heating system becomes too slow to warm up, a system cleanup is required. Yet another common reason behind the need for a power flush is a thermostatic radiator valve which is stuck up in the off position.

Power flushers come in a variety of sizes. A power flusher with a 20 liter tank is big enough for a standard 25 radiator. Power flushers that equipped with a 200 litre tank will comfortably serve very large commercial properties. Many power flushing pumps are equipped with instantaneous flow reversal technology to make their usage and handling much easier.

When do you need a power flush?

There are many instances that could indicate the need for a power flush to clean your central heating system. Some of them have been touched upon earlier, but we attempt isolating them here for better clarity.

  • Noticeable cold spots on radiators
  • Boiler makes knocking, banging and/or whistling (like those of a boiling kettle) noises
  • Frequent boiler break down
  • Central heating takes too long to heat up
  • Radiators transmit much less heat than the pipe work
  • Boiler experiences “cycling” – frequently switching on and off
  • Water from boiler has a non-stable temperature, often switching from hot to cold
  • Everywhere still feels cold even when the heating is on

Benefits of power flushing

Leaving your central heating system to accumulate more sludge, rust and debris over time can damage your central heating system to the point where it becomes uneconomical to repair. At this stage, your system can only be replaced if you are to enjoy any of the benefits associated with owning a central heating system.

A dirty radiator becomes slower in performing its duties, taking longer to heat up, thus increasing your energy costs and system repair bills. Eventually, your pumps, hydraulic systems, heat exchangers and motorized valves will begin to experience mechanical failure. When corrosion becomes too much, holes could begin to appear in your central heating components (radiators, pipe works, heat exchangers, etc.). These holes will provide outlets for the oxide sludge to make contact with other items in your home through leaks and spills. This can be very damaging due to the coloration and chemical composition of sludge.

However, you can arrest the damage early on by power flushing your central heating system. Amongst the improvements to be noted are:

  • Better radiator efficiency
  • Quieter boiling and heating systems – even when operational
  • Disappearance of cold spots on boilers
  • Cheap energy bills
  • Better temperature controls
  • Lesser chances of a break down

How to power flush


Although you can always get an expert to handle the power flushing of your central heating system, you can also DIY the process. First, you will need to turn off all electrical controls and isolate your power supply to the central heating system.

Close the isolating valves present on both ends of your central heating pump and remove the pump from the system. Ensure you close or cap-off any air vents. All diverter and zone valves should be locked open, while anti-gravity valves should be bypassed or removed temporarily. Carefully select the right spot to place your flushing unit such that it is within reach of suitable water feed and convenient water drains.

If your power flusher comes with a connecting manifold, connect it to the central heating system through the heating circulator pump to get optimum cleaning results. You can also connect your power flusher to your central heating system through your radiator valve tails if your flusher lacks a connecting manifold. Be sure to follow the manufacturer’s guide when connecting the power flushing machine to your central heating system.

To summarize, your opening actions should include switching off the boiler, fully opening the radiator valves and diverter valves, and closing off the water supply. If your system is a sealed one, you have to depressurize the system to atmospheric pressure by draining off some of the water present in the system.


You can now add your cleaning agent of choice to the power flush unit and switch it on to have the water circulate the heating system. Allow circulation to go on for about 3 minutes.

Turn on the boiler so that it generates enough heat to activate the chemical cleaning agents and turn it off when the water gets to about 450. Allow circulation to go on for about 15 minutes, reversing the flow every 5 minutes.

After 15 minutes, close and isolate the hot water circuit and the radiators, leaving only one radiator open to allow it flush through. Flush thoroughly, aiding the system with repeated vibrations until the water leaving the radiator is completely clean. Begin with the radiators identified to have cold spots and work your way around until you flush through every radiator.

When you are done with each individual radiator, re-open all radiator valves and flush the system freely until all radiators are completely and visibly clean. Add a neutralizing agent to the water to neutralize the effect of the chemicals.

Test the water for turbidity, continuing to flush until you achieve a reading lower than 100 ppm. Also test for conductivity and ensure you achieve a reading about 10% the value for the mains water supply to your property. Add a corrosion inhibitor to limit the risk of corrosion.

Now your power flush is complete. Disconnect the power flush device and carefully reconnect the circulator pump. Release all valves, reconnect every component of the central heating system, turn on the water mains and turn on the boiler.

Your central heating system is clean and ready for use again. Return all system settings to their original positions. You can now begin to enjoy a more efficient heating system.

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