Someone may pour molten chicken fat down a drain, while a neighbor might flush a wet wipe down the toilet. When the two meet in a dank sewer pipe, a baby fatberg is born.
A fatberg forms like a snowball, as wet wipes get flushed down the toilet and fats, oil and grease get thrown down the sink. They all congeal together and gradually form a hard mass known as a fatberg. And when they get large enough, fatbergs can clog sewers entirely, sending raw sewage gushing into the streets.