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.
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.
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 drain flies that are already there. Also, clean the drains every few months with a mild drain cleaner that is strong enough to remove the scum on the inside of the drain without damaging the pipes.
Kill the drain flies and larvae if they have already infested your home by spraying an insecticide into the drain every day for one week until the flies are gone. Repeat the process every few weeks until the flies no longer return. Follow the proper practices to prevent the flies to ensure the black worms don't return.