My boat (Cherubini H27) has an ugly smelling 'fresh water' tank the PO just used as a non-potable reservoir for washing and general cleaning, never for cooking or drinking. I didn't know why until I nosed around it while pickling for the winter last fall, and it really smelt putrid in there. I'm not sure what kind of material the tank is (it is a metal tank located under the v-berth adjacent to the holding tank (which is some type of Plexiglas or plastic). How best to purge the FW tank and make it potable? Thanks, Bob