John Stumbles wrote in
:

KISS. A rad can be drained from the valve/radiator unions (as long as
there's room to get a shallow tray underneath) and you should have to do
this so infrequently that the added complication (and unreliability) of
a drain cock isn't worth it. Plus they look shyte :-)

This is how I've drained the parts of the system without drain cocks in the
past but we've just got new carpets and with my luck...

Might add the lockshield valves with the integral drain cocks but expect
them to fall to pieces when it comes to using them and so take appropriate
precautions in the form of a shallow tray etc.!

--
F

Beware spamtrap - remove the negative