This is an index of tropes having to do with sewers.

Tropes:

• Absurdly Spacious Sewer: The sewer is oddly roomy considering how infrequently people are actually inside it.
• Bat Scare
• Down the Drain
• Fun with Flushing (sometimes)
• Grimy Water: The gross water that fills a sewer.
• It Came from the Sink
• Pipe Maze
• Rodents of Unusual Size: Giant rats may inhabit the sewer.
• Secret Sewer Society: A society living secretly in the sewers, subways, or other spaces beneath an inhabited surface city.
• Sewer Gator
• Swarm of Rats: Common sewer wildlife.
• Toilet Teleportation
• Tube Travel
• You Dirty Rat!: Rats often travel through sewers, and are accordingly associated with filth and other negative things.