Staining around water heater vent piping?

Is this anything to write up? water heater vent piping leading from
indoor closet to roof. ( Staining )

single wall :roll:

Nice clearance!

Yes. The flashing at the roof may be leaking.

I don’t know Joe, it may have been designed that way to counteract the “too close to combustibles” issue. :roll:

Nah it looks like condensation from the bathroom exhaust running down the pipe:)
Condensation is due to the flue pipe being cold from the open B vent below that is blowing combustion gas on to that insulation at the wall.