X800 will be what is needed.Hmm I guess. Hopefully it's just a bunch of airlocking/some sludge and a good clean with chemicals left to descale the system will be enough. Is flushing the system a hard thing to do (not power flush)? Shall we clean the F&E tank manually (remove any sludge before it's drained?)? Not entirely sure the full process A-Z of cleaning the system with chemicals (something like sentinal x300)?