Rule: Alligators Live in Sewers and Can Come Up Into Your Toilet
False. This urban legend originated in New York City (something about a batch of imported baby alligators flushed down a toilet…), but according to Ian Michaels, spokesman for the city's Department of Environmental Protection, which oversees water and sewer systems, "there are no alligators in the sewers." Alligators are cold-blooded, he adds, and the temperature in the sewers in winter would be too cold for them to tolerate.
Even where one might more reasonably worry about gators―say, in Florida―a call to Frank Calderon, information officer for Miami-Dade County's Water and Sewer Department, yielded a dry "No, no alligators in the sewers" before the question was even asked ("You have no idea how many times people ask us that"). He says that the methane and hydrogen sulfide gases that accumulate in sewers make for an "inhospitable environment." They displace oxygen, so there's none for alligators to breathe; nor is there anything for them to eat. And even if an alligator donned a gas mask and brought its own rations, it would have to be a contortionist to work its way into your bathroom via the toilet. Most sewer-line pipes coming into homes are only four or six inches wide, and the internal trap in toilets makes the opening a mere two to three inches. So you can confidently flush this myth once and for all.