Repair a leaky toilet if you spot moisture on the floor underneath it. What seems like a drip could indicate a serious leak in the progress as the water pools beneath the subfloor, which could cause the ceiling to collapse onto the floor below. Check the supply line to the tank—over time, these can get loose and the seals can wear out. You can replace the supply line yourself for the cost of the $5 part.
The payoff: You could save more than $1,000 in repairs to water-logged bathroom walls and floors, and damaged rooms below.