Outbreaks may last only a few days. They are weak fliers, typically flying only a few feet at a time. They are often found clinging to the walls of bathrooms, kitchens, or in the basement. During the day, adult flies rest on walls or on the sides of tubs and shower stalls. They become more active at night, hovering over drains, sinks and other breeding areas.
Drain flies breed in polluted shallow water or the scum that often collects around drains.
In the house, drain flies lay their eggs in the gelatinous material which accumulates on the sides of drains and overflow pipes, and the larvae feed on the decaying organic matter and microscopic plants and animals that occur there. Adults usually emerge in a week or two. Drain flies can be annoying and do not bite. Control of drain flies should be aimed at control of the breeding sites. The most effective control method is to clean the drain pipes with a stiff brush, removing all the slime in which the flies breed.