W123 SLS line identification and replacement needed
 

Hi-
I've done a search, but I can't seem to find a clear enough diagram that indicates what SLS lines go to what, to and from the valve in the back.

The higher of the two lower lines indicated as supply and return in this picture broke just at the nut point at the flare end. Which is this? Supply or Return?
http://people.oregonstate.edu/~lindgrea/DIY/SLS/1.jpg

What is involved in replacing this line?
Where can I get one or have it made?