Drain cock onto radiator union?

[number49]

Hi All,

I need to do some mods on the heating and have found the combined lockshield & drain cock on my lowest rad is broken (square nut has come out of the drain cock. I assume sheared off by the plumber last time he tightened it up... (yep, him and not me... and he won't be welcomed back )

I've got a new combined lockshield & drain cock to put on, but still need to drain the system to fit it (and do other mods); is there anyway of attaching a hose union to either the TRV or lockshield rad unions to get the water out?

I've had a scout around but struggling to find a clear answer...

 

[number49]

1/2 inch socket & 1/2 inch drain cock???

 

[Charnwood]

1/2 inch socket & 1/2 inch drain cock???

Or 3/4" socket and 3/4" draincock.

1/2" union:

3/4" union: