The Halloween Video Nasty has been posted on YouTube
Video taken from inside sewer pipes lined with congealed cooking fat has been posted on the internet by Scottish Water in a bid to tackle the problem.
Titled Halloween Video Nasty, the footage from the Highlands has been posted on YouTube.
Scottish Water said fats and oils poured down drains were responsible for most of the 3,500 sewer blockages its staff deal with each year in the north.
The agency hoped the video would show the public the damage being done.
A spokesman said: "The scary movie is the latest weapon in Scottish Water's fight to prevent people illegally dumping used cooking greases down plugholes and drains.
"Engineers frustrated at frequent blockages that cause sewers to spill into the environment captured the revolting images using a remotely-operated camera.
"A clip of the footage has been uploaded to Scottish Water's website and YouTube so people can see for themselves the typical state of the public drainage system."
Scottish Water said football-sized chunks of fat had affected water pumps in Thurso.
A blockage in Nairn led to sewage spilling into the River Nairn, which flows towards the town's bathing beaches.
Joanna Peebles, Scottish Water's communities manager for the Highlands, said in some areas of the region staff believed that 90% of the time blockages were caused by congealed fat.
She said: "We're doing the best we can to keep on top of the situation but would really appreciate help from the general public and food establishments.
"At home, cooled cooking fat can be easily scraped into a container or wiped up with some kitchen towel and placed in the bin.
"Businesses are recommended to have proper catering fat traps installed and there are specialist firms that can take cooking oils away to be converted into bio-fuel."
In August, a beach ball-sized clump of discarded baby wipes jammed pumps serving the Carnac sewage plant, which serves 9,000 properties on the west side of Inverness.