I've got a closed central heating system with a combi boiler. I added
some fernox restorer last week and would like to make sure it is all
flushed out.

There are two valves which I used to drain the system down with - but
gravity doesn't always do its job fully when draining it down by
opening the valves on their own.

I thought that if I open both of the draining valves, and then opened
up the tap which I use to top up the closed system with water, would
that effectively flush out the whole closed system.

Am I being naiive? :-)

If not, what would you all suggest as the best method of fully
draining the system?

Thanks,

Aris