Vegetable oil costs about $5 per bottle. For a year of daily dumping, that would come to over eighteen hundred dollars. You can get about 200 yards of dental floss for about $3 per roll. For a year of dumping that, it would come to just over a thousand bucks.
Add in tax and you come up to about $3,000 per year just to foul up the city's sewage system.
I know a fellow in prison (completely un-named, of course) that spent months taking prison bed sheets, one per week, ripping them into half inch strips and flushing them down the toilet. I had... rather, I'm sure he had lots of fun doing it, but it only stopped up the plumbing for an hour one day.