Powerflushing is purely and simply a way of removing the rust that slowly builds up in your heating system and boiler over time. Water, chemicals, powerflush equipment and an experienced operative are used to do a power flush.

If you have seen someone else’s system powerflushed you will know what an amazing amount of stuff can come out, in all shapes and sizes. But, contrary to popular belief the vast majority of the sludge that you see does not come from your boiler. Most non-condensing boilers (those installed before 2006) have cast-iron heat exchangers and they, by and large, do not rust. The vast majority or rust and/or sludge in your heating comes from the radiators themselves as they are made from mild-steel.

Water is made of hydrogen and oxygen (one part H and two parts O = H2O). Oxygen is highly reactive and is always looking for somewhere to latch on to instead of the Hydrogen molecule. So, any time it comes across a piece of iron that is ‘bare’, i.e. unprotected, it is going to latch on to that and makes rust (most often Fe2O3). And that’s where rust comes from. Power flushing radiators will remove that.

Once you have had a power flusher in to do the work for you, the best way of protecting your system is to have the heating system regularly topped upped with corrosion inhibitor. These stop the rust forming by adding a protective molecule to any exposed bare iron. That molecule (most often a form of another metal called molybdenum) parks in the place that the oxygen molecule would want to be. And the result is no rust. The only caveat to this is if your heating system has a design flaw in it and is pulling in fresh water all the time.

Yes, there are other ways, but they are nowhere near as effective as using a power flush machine when it is used by a competent and experienced heating engineer. You can add any chemical cleaner in to the system, leave for up to four weeks (Warning:careful here if you have micro-bore pipework) and then open up the system drain-cocks and let the water run out.
When you do that the only force moving the water out of the system is gravity and that will not pick up any larger bits of rust. Those will be left in nooks and crannies.