Like FDPOWERFLOW said....i practically powerflush for a living and find that i can take massive amounts of sludge out of a system using a combination of my powerflush machine, i run 2 in-line filters(just to make sure), vibraclean,infared thermometer and tds + ph meters.
When flushing a combination system i always cut into the flow and return to isolate boiler from the system and heat the water with what is in effect a immersion heater. Using all this i beleive you get 90% of the magnatite out the system and will always advise customers to have a magnaclean/tf1 fitted as a safe guard to their system.
I however will not entertain powerflushing a system with 8mm piping on as you will not get the velocity of water rushing through the rad to make the flush effective....i always tell my customers they'd be better off upgrading the pipework to get the system running more effectively. 10mm pipe is just about ok as long as there is no kinks in the pipework.
I have spent 45mins on cleaning just one rad at times and had to clean my filters out after doing this!!
everybody has their own preferred methods and there is no right answer.
