What size of spanner do I need to fix this leaking radiator?

[Yorkshire Tea]

Hello,

I have a leaking radiator nut. Can someone please tell me the correct size of spanner I need to tighten up the nut? (I am sure "nut" is not the correct term!)

The attached image shows the nut and you can see the drop of water on its underside.

I have a set of spanners with number on them up to 17. However, 17 is too small to fit around the nut.

Alternatively, should I be mending it in another way?

Thanks.

 

[oldbuffer]

Assuming it is the hexagonal nut with the drop of water on it, then 1/2" BSP (or BSW). They are an imperial size, not metric. Best bet is a decent medium sized adjustable spanner (e.g. Bahco). You'll need another spanner or grips to hold the body of the valve while you tighten up the nut.

There is a chance the leak is from the tail where it goes into the radiator. That's a different issue, and a bigger problem. You'd have to shut off both valves, empty radiator, remove the valve in the photograph from its tail, remove the tail, clean the tail and the female thread in the radiator, re-wrap the tail with 15 (or thereabouts) wraps of PTFE and screw it back into the radiator, tight. Then valve back on, open the other end valve to the same point from which you shut it off . Open valve and check for leaks.