Black worms can gather around your sink drain.
Black worms may begin to show up inside and around the opening of your sink or bathroom drain. These black worms are actually the larvae of the drain fly. Drain flies survive off organic matter, soap scum and mineral residue inside drains and can become a nuisance in your home.
Drain Fly Identification
Drain flies are no longer than 1/6-inch long. They have dark gray or black, fuzzy bodies and long antennas. Their eggs are small and are either brown or cream colored. The fly will lay 10 to 200 eggs at a time. When they hatch, the larvae are 3/8-inch long. They are gray with ends that are slightly darker than the middle and can resemble worms.
Growth Conditions
Drain flies will lay eggs in certain conditions. If you don't use your bathroom sink very often, water will be left standing in the pipes and will attract the drain fly, which will lay its eggs in the sink. The fly also likes to lay eggs in the slimy coating on the inside of the pipe. Once the fly lays its eggs, they will hatch in as little as 32 hours. The larvae will thrive on the slippery scum that often lines pipes.
Prevention
Prevent the black worms from developing inside your drains by turning off your water whenever you shut up your home, which will prevent water from dripping through the pipes and encourage whatever water is there to dry out completely. If you can visit the home to turn the water on frequently, it will do much to remove
Control
Kill the drain flies and larvae if they have already infested