Every year 'fatbergs' cost water companies millions of pounds to clear.
They're build-ups of fat, oil and grease that block drains.
But fear not, because there's a detective on the streets who "nose" how to sniff out the problem.
Hector, a nine-stone former police dog and his owner Steve Williams, have swapped a life fighting crime to one fighting grime.
They go by the name of the FAT detectives - a badge they wear with pride.
Check out Martin's report.