Opps... Sounds like Catalina forgot to finish...
installing the vents.Hi, Donna--To the best of my knowledge, all tanks vent overboard for obvious reasons -- one of which you describe. Suggest that you call Gerry Douglas at CatalinaYachts and ask him where the tank should vent to. He designed the C-400 so he should know. I suspect that a worker went to lunch, forgot to finish the job and it wasn't picked up. If so, Catalina will certeinly take care of putting things right.Good luck--Ernie April