Flushing a system

[Bogart]

As I am not on mains drainage, I have a treatment plant, any suggestions as to how to flush a system out. I am shortly going to install some new radiators but am worried about the flux that may be introduced into the system.
I am installing 11 rads. Is there anything that I can attach to the pipework to extract the flux or am I worrying about nothing?

Thanks

 

[WC1]

If the system is pressurised, fill and drain with fresh water. Run it out into the garden or rainwater system if you don't want it in the treatment plant. Good idea to get the flux out, its very acidic.

 

[Bogart]

There is no rainwater system. I would have to dump it into a meadow which is not very environmentally friendly or correct