Leaking Halstead platinum

[disponded]

Hi all
I have a Halstead Finest Platinum fitted in the house and have had a problem with pressure dropping every so often but no sign of a leak.
I have now discovered a leak from the fill loop valve nut as in the picture.
I think the connection will clean up ok and I'll be able to reseal the nut, but incase it doesn't go to plan I was looking in vain on the net for a spare valve. For some reason I can't find one.
Anyone know where I'll find one and is it actually called a fill loop valve? Also what's it's purpose? Is it a non return valve?
Thanks for your help.
http://www.flickr.com/photos/82775580@N05/7622707694/

 

[Boilerman2]

Sorry to burst your bubble, but the leak shown in your pic is upstream of the filling loop, and therefore cannot cause a loss o pressure in the primary water system, things to check - AAV's on the boiler for leakage, the Expansion vessel for correct air charge

 

[disponded]

Thanks Boilerman
I will check out the air valve and tank for leaks.

 

[disponded]

I drained down the system and re pressurised the PV, took the leaky joint to bits and found the washer was disintegrated. I refilled the system and the pressure is holding for now.
I'll see what the pressure is like over the next few days and I'll get a new washer and fit that too.
Thanks for the help.