For example, in a case like this, I would: 1) make sure all new tenants complete a "Rental Move-In Checklist" with a section that specifically addresses the condition of the bathroom/kitchen sink, toilets, etc; and 2)  include the following clause in my lease:"LANDLORD WILL NOT BE RESPONSIBLE FOR DRAIN BLOCKAGES AND BACKUPS IN THE KITCHEN SINK, GARBAGE DISPOSAL, DISHWASHER, WASHER MACHINE, TOILET, BATHROOM SINK AND BATHTUB CAUSED BY GREASE, PAPER, FOOD, HAIR, OR ANY OTHER FOREIGN OBJECTS.