Quote Originally Posted by JLMCDANIEL View Post
There's no black on the cold water lime or the hot water line in the same area which suggests to me that it has more to do with technique than environment.
Maybe because THEY ARE BELOW the BREACH in the Vent Connector at the bottom of the offset!

I was addressing oldhanggliderpilot. Let pilot determine. Could just be how it LOOKS in the photo. Either way the breach should be FIXED and a slope on the lateral.