Firstly I don’t mind DIYers, if people want to DIY that’s fine and it’s something new to learn. I am a power flushing expert and a member of the power flush association. My clients simply don’t want to, or failed trying to power flush.
Fact:
Using a de-sludger will get the sludge all loose and it will ALL drop of the internal walls, of the system and just lay there at the lowest points. Sludge is metal and heavier than water and will need high flow rates and velocities to move around, which your pump cannot do because that would make it in-efficient and costly to run – so it can’t by design. It is also not supposed to, as your system is not supposed to have sludge in it.
If your problem is really bad: (tons of sludge on internal walls over many years)
Draining it down will not do anything, the sludge will be lying on the bottom of radiators, pipes and boiler and is more than likely to cause you trouble as the pump moves some of it to even lower points with less flow – causing even less flow. But that does not mean you can’t try it, if it fails get a professional; at least it is all loose and ready to be removed.
Is power flush a DIY job:
1) Only if you know how to remove and fit back a radiator and fully understand your system. You can break a boiler if you use a large power flush machine (like the ones you rent) and close the wrong valve at the wrong time on certain boilers.
Flooding is also a real risk if you get it wrong, but normally it’s something you notice quickly and can turn the machine off.
2) and have a system that is all working fine. It's 10 times more complicated to flush a system that has problems, and you need experience to know how to treat each different problem.
Power Flush Guy, November 2011