Water heater vent leak?

[dgilber52]

I have the attached reddish brown stain on my ceiling adjacent to wall of the fireplace (which has a wood burning insert). The roof has been gooped and the chimney in the attic shows no water leakage. The gas hot water heater is vented thru the roof parallel to the fireplace flue. I've been told that the color of the stain indicates natural gas leaking, likely from the water heater vent before it goes through the roof. The offered solution is replacing the vent from the ceiling to the basement location of the heater.
First of all, does this all track as an accurate problem and solution. If it is gas leakage, does changing the vent to a through wall vent with fan make a cost better effective choice?
Thanks

 

[breplum]

Water, yes. Gas vent: not possible to use that assessment.
Fan forced tank water heaters are not worth the price any more due to the relatively short lifespan (6yr pro-rated tank warranty).
Tankless would be a better investment, and you get 96% efficiency for condensing tankless.

 

[TomFOhio]

Or you could put in a vent liner kit and then there would be no fittings.

 

[Twowaxhack]

Tan/brown stains on drywall happens from all types of leaks.

Whoever told you the color of the stain indicated leaking condensate is poking and hoping.