A reader has written to us all the way from Tasmania, Australia. He would like some information about some worms that he found in his toilet. He says that they are all less than one-inch long, very skinny, and appear to be living quite happily in the toilet water.

He has helpfully included the following picture:

The reader notes that it was nighttime when he found these in his toilet. In addition, the reader and his dog (who has been dewormed) are the only ones who live in the house.

Well, we have good news. These worms are unlikely to be related to either the dog’s or the reader’s gastro-intestinal systems. Instead, these are likely the larvae of the common black drain fly.

The drain fly comes from the family Psychodidae and could be one of any number of species. Drain flies are harmless, but they tend to be one of the more emotionally disturbing creepy-crawlies that we find in our houses. However, the larvae are actually quite helpful, eating decaying matter from within our pipes.

Still, if the letters we get are any indication, most of us don’t want these drain flies living where we live, especially in our toilets or shower drains. The good news is that, like most of the critters we write about here, the drain fly larvae will go away if you take away their food. The bad news is that it can be difficult to take away their food, since typically they’re eating something that is not easily visible.

Our advice to him is that he clean the pipes where he is finding the larvae as thoroughly as possible. First, he can clean his toilet normally, and then scrub the pipe up and down with a metal pipe brush. Once he’s scrubbed the pipe thoroughly as far down as he can reach, he can try pouring boiling water down the pipe (obviously, it is important to use caution to avoid spills and burns any time one is working with boiling water).

If this does not alleviate the problem, then we do not recommend that he use any chemical remedies without first contacting a local pest control professional. The professionals in his area will be familiar with the species that are common to that area. A professional will also know how to eliminate the pests effectively without posing a threat to the people and animals living in the house.

Originally posted 2017-02-03 12:00:54.