Draining radiator, how to open value?

[gmc]

I need to drain my radiators to put inhibitor in . I've located the one and only radiator with a drain tap, but I can't find the value to open the tap.

Looks to be this one:
Radiator Drain Off Valve - 1/2" BSP


But for the life of me I can't work out how you open the value. There is nothing behind the value.

Do you maybe turn the ring at the bottom? I don't want to turn something that's not supposed to be opened.

 

[JCplumb]

There will probably be a valve you can turn with a bleed key inside the hose spigot.

 

[ShaunCorbs]

Undo the spigot eg the barbed bit but the washers prob stuck

 

[gmc]

Undo the spigot eg the barbed bit but the washers prob stuck

Thanks, I've unscrewed the spigot. You were right, washer is stuck.

 

[ShaunCorbs]

Thanks, I've unscrewed the spigot. You were right, washer is stuck.

No 8 screw into the hole bucket below pull screw out with washer hopefully on then insert barb back in with hose pipe while water is coming out