Like the Fruit fly, most of the time Drain Flies are a clean up problem where professionals are not required. Drain Flies require a source to reproduce, source being an area where decomposing organic materials are found. E.g. Damp rags/mops, plumbing leaks, plumbing drains (most times rarely used fixtures or basement floor drains,) over watered house plants, stagnant water. If sources are cleaned up and removed the problem will generally resolve itself.

Adult drain flies are small, fuzzy, dark colored insects with the body and wings densely covered with hairs. Their wings appear large for their body, are held roof like over the body when at rest, giving them a moth like appearance. They are weak fliers and fly only a few feet at a time. Larvae are legless, about 3/8 inches long, wormlike and gray, with both ends somewhat darker.