Water in your system reacts with the steel in radiators to create a black inky like sludge called magnetite. This product of internal corrosion of the radiators has the disadvantage of blocking valves, boiler parts, pipes and radiators making the system less efficient or, if the water in your system is very contaminated it can cause the heating system to fail.
Sludge in your heating system can cause to blockages and corrosion which will lead to both inefficiency and / or breakdown. In extreme cases it can be so damaging that a complete boiler replacement is needed.
Parts that are particularly susceptible to ‘sludge’ in the system are the boiler’s heat exchanger, radiator valves and the impeller on the system pump. Reducing the useful cross sectional area of pipework, it can also prevent the free and efficient flow of hot water around your system. As sludge settles in the bottom and middle of radiators it prevents an even heat distribution and radiators will be slow to heat up. Over the summer season while radiators are not used, sludge can settle at the bottom of rad valves so that, come the autumn and radiators are switched back on, some will not work or will not get to proper temperatures. It is common for some rads to be much cooler at the bottom and middle because of sludge buildup where flow is weakest through the rad; hot water rises as it pumps through the rad and sludge build up prevents an even flow through the whole radiator.
Blocked heat exchangers in your boiler, including the plate heat exchanger on combi boilers restrict or prevent free flow through the boiler as the water is heated; this causes the boiler to overheat and the boiler to switch off heating as the thermistors detect that the water has already reached very hot temperatures. Other symptoms of a blocked plate exchanger on your boiler include varying temperature of water at hot taps caused by an uneven flow through the system.
When Do You Need A Powerflush?
If you are having a new boiler installed with old radiators it is necessary for the system to be powerflushed otherwise any manufacturers warranty will be invalidated.
Many monthly service and breakdown plans will not cover your heating system for any callout if sludge is found to be the cause of any fault found at diagnosis. It British Gas Home plan or Corgi find out that there is sludge in your system they will require you to present an invoice showing that your heating system has been powerflushed.
It is a very good idea to consider a powerflush if your boiler and system is more than 5 years old; especially if any water bled from the radiators is grey, orange or even inky black in colour. There are also sludge detector kits that can confirm the need for a poweflush. You need to test your system every 5 years to see if a powerflush is required.
Signs You Need a Powerflush
As mentioned before, here are signs to look out for that suggest that all is not well in your central heating system.
Cold areas on radiators e.g. at the bottom
Excessive noise from the boiler or the heating system pump
Discoloured water when you bleed the radiators
Heating is slow to warm up
Cloudy tap water (limescale in system)
Some radiators struggle to heat up as well as others
Radiators cold but pipes are hot
Boiler regularly shuts down and needs restarting
No water escapes when you bleed a radiator
Noisy radiators and or / boiler
Small leaks in radiators.
What Are the Benefits of a Powerflush?
It’s not all doom and gloom; there are lots of positive reasons to get a Powerflush carried out too.
Radiators will heat up quicker
Radiators will get hotter
Quieter radiators / boiler
More energy efficient system = cheaper energy bills
Higher hot water temperatures
More reliable i.e. less chance of breakdown
Increase the life of your heating system.
How Does a Powerflush Work?
A dedicated powerflushing machine is connected to your system, via a pump or by a flow and return on a radiator. This powerflushing machine will then fill your system with new water and, at the same time, drain your system of that old water. Once the system water flows much clearer, the system drain is removed and a cleaning chemical is added to the water so that the powerflushing machine can circulate the cleaner, while heated, through your whole system. Individual radiators are vibrated with dedicated tools to dislodge well settled sludge in the bottom and middle of blocked radiators. The system will be systematically open and closed down to focus on one radiator at a time. Once the cleaner has been run through the each rad for previously determined period of time according to the cleaner and the machinery being used the system is once again flushed through with clean water until all sludge and cleaning chemicals are washed out of the radiators, pipework and boiler.
The process can take 6+ hours and is a labour intensive task. A larger house with lots of radiators may require a second day of work.
Who Should Carry Out a Powerflush?
Plumbers can carry out power flushes but it is likely that at some point your boiler will require attention. Part of the reason for the powerflush may be that the boiler has broken down. The boiler may also have air in it when the system is refilled. It is therefore considered essential that your plumber is also qualified to repair and address any boiler issues during the power flush.
How Much Will a Powerflush Cost?
Although a clean and efficiently circulating system will save you money so will the necessary powerflush to get a failed system working again. A powerflush can range in cost from £300 to £1000 depending on the size of the system, the quality of chemicals used and the area that you live in.
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