Fuel tap leaking

Hi all I wonder can anyone tell me what the small nipple on the fuel tap is for found when the bike is sitting it’s leaking fuel from this small nipple

It's the vacuum hose from the inlet manifold?

Jameshambleton wrote:It's the vacuum hose from the inlet manifold?

Sorry not that one the much smaller one it’s only a few mm in size I’ve got the fuel pipe and vacuum pipes connected this other one doesn’t seem big enough to connect anything to

Also while I’m talking about the fuel tap does anyone know the size of the copper pipe that runs into the tank mine is pitted with small holes

I had a similar problem with the "copper pipe" on my fuel tap...................  used a soldering iron and ran a thin film of solder over it to seal all the holes.  I'd guess you could probably use epoxy resin if you haven't a soldering iron.