drain sealed cH system

Nigel Smith

I am planning to drain my combi-boiler CH system to fit TRVs to 8 of the 9 radiators. I intend to drain the system using the drain tap, replace the radiator valves, refill the system using the loop, and add corrosion inhibitor via a radiator valve using a kit from Wickes.
Is there anything I should watch out for?
I note that some sources say that you should not a ttempt to drain a sealed system without professional help!