Q. We just had a plumber out for a clogged drain and he told us that we had drain flies. What in the world are drain flies and what do we do about them?

A. Well, the name says it all. The larvae (maggots) of these flies actually do live and feed on the crud inside drains, especially scummy drains that need a good cleaning. No offense – not one of us can claim pristine drains! The female drain fly lays her eggs in this rotting, slimy, oozing, gelatinous muck or scum that builds up in drain pipes.

Adult drain flies are tiny, dark flies that fly in short hops or hover around drains. They’re also sometimes called moth flies because they have hairy wings like a moth, although they are much smaller (see an illustration in our Pest Library, under Flies). You’ve probably seen a few drain flies resting on walls in your bathroom around the sink or tub and didn’t pay them much attention.

Getting rid of drain flies isn’t as easy as you would think. The larvae can survive household drain cleaners, soaps, bleach, and boiling hot water. As long as there’s a film of scum left down in the drain, the flies will continue to breed and thrive. The best control is a thorough, deep cleaning/degreasing of the drains followed by the use of a specialized enzyme or bacterial product that dissolves any remaining scum left in the pipes.

Drain flies can breed in sink, bathtub, and shower drains, as well as in sump pumps, basement floor drains, even in scummy garbage cans or refrigerator drip pans. Call the experts at Colonial. We will conduct a thorough inspection to determine the source or sources of the drain flies and can institute a specialized cleaning/treatment program for affected drains.