Turn off the boiler. Drain the system. Do your work.Put in inhibitor via a
radiator ( a bit tricky ) then refill the system via the filling loop which
should be near the boiler Take the pressure up to approx 1.5bar ( gauge on
boiler )
Check for leaks. Good Luck

"Nis" wrote in message
oups.com...
I am about to drain my Dads central heating radiators (to move pipes to
build a cupboard). I've drained rads before with conventional systems
with header tank, and refilled with inhibitor. Can anyone advise me
what to do with a combi boiler. My Dad says theres no header tank, so
does the system use inhibitor? Where do you put it in? And do you have
to isolate/drain the boiler to drain the Rads?
Any help would be much appreciated
Nis