This report followed Thames Water as they went down into the sewers of London.
Huge lumps of oil and grease caused by pouring hot fat down the drain are costing water companies around £79 million a year to tackle.
The BBC's John Maguire takes a close look at "fatbergs", which are causing problems in London's sewers.
View the full video report here:
Thames Water using the Open Drum Winch and Lightweight Tripod in London, UK.