Drain flies are similar to gnat and house fly fusion. They don't bite or sting (although they might pass dangerous diseases ), and are more of an aggravating nuisance than anything else. However, they are also a signal of a potential plumbing problem. Drain flies multiply around flat water and live off of the goop flat water creates. They are at times tricky to eliminate because they are small and their eggs are tinier. However, by figuring out the spot that the breeding ground is and getting rid of the plumbing concern (and the goo ), you will be able to get rid of the bugs in a couple of weeks. To prevent the flies altogether, though, do simple check-up of all of the places in the house that may accumulate still water. These places consist of any drains, garbage disposal units, the washing machine, refrigerator, and commodes. To find out more about drain flies, look at this website.