Morning people, I’m in the middle of a listed building refurb. The customer is having overlay ufh throughout and using the original cast iron rads as the supplementary heat. I’m removing the top and bottom entry bushes to have them at the bottom, there’s lots of dried magnetite coming out. I’m thinking of hooking up a powerflush machine whilst we’re at building stage to clean them. I’ve put some of the big lumps into an acid/ water mix and it’s not limescale . What chemicals would give satisfactory results on cold water powerflush?