winterizing-leave fresh water tank open or closed?

I disconnect fresh water tank from Plumbing. There is always some water in the tank specially since I do not level my MH for the winter and I feel that since the plumbing is below the tank the potential for water to get into the plumbing and freeze exists. I flush the tank before use the next year. You could tape over the outlet I suppose but I do not. If worried about bugs spray the area before closing for winter