Casual Person

Question: There's something that Bilbo says that confuses me greatly. When he's speaking to Gandalf about how mad he is at the dwarves for invading and destroying his house, he says something like, "I won't even mention what they've done to the bathroom. They've all but destroyed the plumbing." I'm pretty sure that toilets and plumbing weren't invented back then. They used chamber pots or went outside to do their business. So what is Bilbo talking about?

Zinka17