What size is this rad/valve connection? picture included

[Last Plumber]

Take the rad off and the nut will slide off the tail, (the bit in the rad)
Once you have the nut, put a 5p inside it and then a 1/2" tap washer and use that!
That's what I always do and it never fails.

finger tight will do, maybe a 1/8th nip, I always open the valve to make sure it doesn't leak.

 

[Harvest Fields]

Take the rad off and the nut will slide off the tail, (the bit in the rad)
Once you have the nut, put a 5p inside it and then a 1/2" tap washer and use that!
That's what I always do and it never fails.

finger tight will do, maybe a 1/8th nip, I always open the valve to make sure it doesn't leak.

So your the one

 

[Last Plumber]

So your the one

AYE !

 

[Last Plumber]

Are you the one who owes me £100 in 5p's and £50 in Washers?

 

[Chuck]

put a 5p inside it and then a 1/2" washer and use that!
That's what I always do and it never fails.

And invoice as:

Install 5p coin as blanking disc; parts: 50p, labour: £3.

I assume ? The look on the customer's face when they read it must be priceless!

 

[Last Plumber]

And invoice as:

Install 5p coin as blanking disc; parts: 50p, labour: £3.

I assume ? The look on the customer's face when they read it must be priceless!

It's the knowledge, skill and experience they pay for chuck!

 

[Last Plumber]

Install 5p coin as blanking disc;

I prefer:-
Provide and install Coin of the Realm depicting a portrait of Queen Elizabeth the second. The coin is professionally set upon a Black Vacca washer which is artistically embossed with the words '1/2" Vacca'

 

[Last Plumber]

That's got to be worth £100

 

[Best]

Maybe that valve has the large flange tail?
Was more common on the older TRVs and on the valves with option for copper or iron pipe, which that is.
The photo is difficult to judge, but the more I look at it, the more I am sure that tail nut is the large type.

 

[Best]

I prefer:-
Provide and install Coin of the Realm depicting a portrait of Queen Elizabeth the second. The coin is professionally set upon a Black Vacca washer which is artistically embossed with the words '1/2" Vacca'

You really should always do all your work to a gold standard and use a gold half sovereign.
Expensive, but it will always impress the person that removes the blanking nut.