1) Buy some INSULATED flexible ducting at the Home Center. 2) Make sure your bathroom is ducted to the OUTSIDE and NOT just inside the attic.
What's happening is the warm, moist air is condensing on the cool surface of the duct and dripping back into the bathroom. Doing as I described should fix your problem.
My best to ya and hope this helps.
Jay J -Moderator
PS: Be sure to measure the diameter of your current duct before you go to the store, and the length ...
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