Confused with rad pipe connection

[kasser]

I've got a radiator with two dissimilar ends where the pipes are connected. One end is familiar to me, it's 15mm diameter, bit of pipe with olive and nut and the whole thing has been screwed onto the radiator. You just need to screw the TRV or lockshield valve to it.

The other one is new to me. It is much larger, looks like 22mm, still bit of pipe with an olive at the end, but as the pic shows, it doesn't seem to have been screwed onto the radiator but seems like an extension of the radiator. The nut is too big for the valves I have. How do I connect it to the valve? Why is it so large here? I can't even unscrew from the rad to replace...

 

[ShaunCorbs]

http://www.NoLinkingToThis/p/chrome-angled-radiator-valve-drain-off/70408

 

[king of pipes]

Just a different type of valve thats all some can be removed with large allen type key others need a specialist rad key but it is removable cheers kop

 

[snowhead]

The second photo is the original valve stem.
The other end, first photo, has been removed in the past either to fit a Thermostatic valve or a standard valve to replace a leaking one.

If you look in the end of the stem, it's either hex shaped or has 2 protrutions inside.
This tool does both types of fitting;

Step Wrench Radiator Spud Wrench 1/2" Dr. Valves Lugs Nipples Tank Connections | eBay

 

[kasser]

The Screwfix link helps, thanks. I suppose the TRV for the first pic would be 15mm at both ends?
I didn't know you could remove the valve stem. All of the radiators I've come across (i.e paid attention to) was like in the first pic.
I'll have a look inside the stem tomorrow.
Cheers guys. Always learning something new here.

 

[firemant]

http://www.NoLinkingToThis/p/radiator-spanner/11467

 

[moonlight]

might need a key with the slots in it.

 

[Ric2013]

'All' radiators come with a 1/2" BSP female connection and the tails come with the valves.

 

[BLOD]

'All' radiators come with a 1/2" BSP female connection and the tails come with the valves.

And then there's the other ones that have much larger and sometime left or right hand threads