We have at least one dramatic ancient story that illustrates the danger of hooking your house up to a public sewer in the first or second century AD. The author Aelian tells us about a wealthy Iberian merchant in the city of Puteoli; every night a giant octopus swam into the sewer from the sea and proceeded up through the house drain in the toilet to eat all the pickled fish stored in his well-stocked pantry.
— What toilets and sewers tell us about ancient Roman sanitation