You might have a drain fly problem if you’re doing the dishes and notice fuzzy flies the size of a shoestring flying out of your kitchen sink like fireworks on the Fourth of July. — Drain flies, as their name says, reside in drains. Drain flies are around 1/16–3/16 inches (1.5–5 millimeters) long, with six legs, a pair of wings, and antennae, like most flies. Their skin is a pale gray or tan color.