What is power flushing? Quite simply, a means of cleaning a wet central heating system by using water and cleaning chemicals pumped around the system at high speed but low pressure.

The power flushing equipment consists of a container to hold the water and cleansing chemicals, a powerful pump to circulate the water and various hoses and valves to connect to a heating system and be able to alter the direction of flow to loosen contaminants within the pipwork and radiators.

That’s it, a fairly simple process, but one that needs to be carried out carefully to minimise the risk of spillage and leaks. Also one is dealing with potentially dangerous chemicals, especially the acidic ones.

How does it work?

The power flush machine is connected to the system by either removing the pump head and connecting via an adaptor or more usually by removing a radiator and connecting the hoses to the flow and return radiator valves. A hose is also fed to a drain point so that the dirty water can be dumped into the drains.

The machine I use has a 1.5hp motor and a diverter valve which means that the water flow direction can be instantly reversed to facilitate in removing sludge and debris, in effect “swilling” the water in the system back & forth to loosen debris.

Various chemicals can be added to assist in removal of debris including acid based chemicals for stubborn systems, these are then neutralised to prevent acid based corrosion. These are really only used on old systems where there is also scale build up.

Another way to loosen the scale is to vibrate the radiator with a rubber mallet fitted to a hammer drill, this is done when the flushing takes place to loosen debris. The flow of a central heating pump is not sufficient to loosen sludge inside a system and that is why a power flush machine has to be used. Once completed and a magnetic filter fitted, corrosion can be minimised, provided that inhibitor levels are maintained.

System was filthy due to constant dilution of inhibitor

This is my Power flush machine

The picture on the left shows my flushing machine in action, the flow and return pipes are connected to the valves of a radiator which was removed prior to a new towel rail being fitted. The dump pipe was put into the WC so waste water could be easily disposed of. The magnetic filter stops sludge entering back into the system.


Image showing effects of sludge in radiator

The picture on the right shows an illustration of how sludge build up in a radiator can reduce flow and heat output. Imagine the effect when all the bottom of the radiator is silted up!
A similar thing occurs in the passageways of a plate heat exchanger in a combi boiler, but these are very fine so can easily block, replacement exchangers can be between £100 and £200 + fitting.

Hopefully after reading this you now appreciate why power flushing and magnetic filters are a necessary part of central heating maintenance and protection.

See also the post about Scale Inhibitors

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