Take the plunge [InvestiGators Volume: Book 2]by Green, John 

BTSB Prebound(First Second, 2020)

BTSB #: 395750 Available

Dewey: 741.5/NAges: 7-10   
AR: 3.6 MG Lexile: 410 HL

Genres:

Subjects: Alligators - Fiction Spies - Fiction Humorous fiction Sewerage - Fiction Graphic novels

Summary: S.U.I.T. headquarters is under attack, and Mango and Brash are going undercover and under ground disguised as city sewer workers to unclog a sticky situation. But when their search for the criminal Crackerdile backfires, the toilets they travel through back up-and the InvestiGators take the blame for it! Can Mango and Brash restore their good name and put the real culprit behind bars before the whole city is in deep water? In graphic novel format.

Toilet vortex [Fart Squad]by Pilger, Seamus 

BTSB Prebound(Harper, 2016)

BTSB #: 717988 Available

Dewey: FAges: 7-10   
AR: 4.6 LG Lexile: 690

Genres: Humorous Fiction

Subjects: Humorous fiction Plumbing - Fiction Sewerage - Fiction

Summary: When Janitor Stan goes missing, the Fart Squad follows their noses to save him. But what they discover would make a plumber lose his lunch. Stan has fallen through a toilet vortex and into the land of former fajitas and digested donuts where the Royal Flush reigns supreme.

Undertown by Bukiet, Melvin Jules 

BTSB Prebound(Amulet Books, 2013)

BTSB #: 169884 Available

Dewey: FAges: 10-14   
AR: 6 MG RC: 6.2 6-8 Lexile: 900

Genres: Adventure Fiction

Subjects: Adventure fiction Sailing - Fiction Sewerage - Fiction Homeless persons - Fiction New York (N.Y.) - Fiction

Summary: Middle schoolers Timothy Murphy and Jessamyn Hazard careen downhill on a sailboat which was being towed through Manhattan and fall into the sewers, where they meet interesting characters before being caught by the evil "queen" of this underground society.