I'm going to power flush the CH system next week.
Cleaning agent gone in today.

The system has a one year old condensing boiler,
and is a conventional 3 port valve job for CH and
hot water cylinder. There is a roomstat and all except
one of the radiators has a thermostatic valve.
The original system was installed in the late sixties.

I've never done this before - any general advice?

Thanks,
Roy