Neither do underpants.
Yes, true story—this one out of the UK—Severn Trent Water reports that a sewer in the town of Shropshire was clogged and causing backups, until crews discovered and removed the culprit: "piles of pants that had been flushed down a toilet, somewhere nearby."
|Image courtesy Severn Trent Water
In the words of their customer operations manager, "How on earth people have managed to flush this amount of underwear, I don’t know. ...[This] is just one example of amazing things we find blocking the sewers."
The story goes on to summarize a useful reminder to customers: What you flush matters, and when you use the toilet as a trash can, problems follow. We have a handy list of 15 things you shouldn't flush, but there are others.
Boxer briefs is one of them.