9 Causes Of Black Worms In Your Sink (& What To Do)

If you’ve ever come across black worms, be it big or small, anywhere around the sink drains in your bathroom or kitchen, this means you possibly have a drain worm problem. These worms are a terrible nuisance as they can be the potential cause of spreading bacteria in your house and carry a lot of health-related risks. These worms develop as larvae of the drain fly, which feeds off the soap and other detergents that go through the sink drain. To get rid of these, there are a lot of cleaning tricks and home remedies you can use. 

This article will tell you all about black worms, why they grow and develop in sink drains, and all the ways you can get rid of them and keep your home safe from health risks. 

What Are the Black Worms in My Sink?

The black worms gathering in your sink are actually the larvae of the drain fly. A drain fly, also called a sink fly, is an insect that primarily lives on organic materials found in sewage or sink water. These sink flies also use the standing water and moisture in sink drains as a breeding ground; they gather, mate, and lay eggs in the slime formed by contaminated water. 

These eggs become the larvae, also known as the black worms that you see loitering around in your sink, and turn into drain flies later on. These worms are legless, and most of them are very small even when matured, being only 4-10 mm in size. These slender-looking worms feed on the contaminated water and are a very shiny black in color. 

These black worms also have the tendency to carry bacteria and germs which can possibly contaminate your house, so we suggest taking care of them as soon as you can. 

Why Are There Little Black Worms in My Sink?

Less Usage of Bathroom or Kitchen Sinks

If you don’t use your bathroom or kitchen sink very often, there will be water left in the drain pipes since it’s not being drained out by usage. The standing water and slimy coating of the pipes attract the drain fly. This becomes the perfect ground for drain flies to produce black worms, which gather in the sink. 

Standing Contaminated Water in the Drains

Drain flies loiter around the spaces where there’s water left standing. So if your pipes have a space inside where there could be puddles of contaminated water, it presents a perfect breeding ground for drain flies. The black worms also feed on the organic matter present in the contaminated water. 

Presence of decaying organic matter

Black worms survive off of decaying organic matter, so if your sink has a problem where the matter accumulates at the bottom, the chances of an infestation are high. The worms thrive in places where there’s an abundance of rotting or semi-liquid organic matter, such as sink pipes. 

Less Regular Cleaning of the Sink Drains

If you haven’t cleaned your sink drainage and pipes for a while, this could be a big cause of the black worm infestation perpetuating to the point where the worms now appear in your sink instead of staying inside the pipes. The sink drainage is the hub for all things contaminated and decaying and is the perfect place for drain flies to breed, resulting in more black worms. 

Failed Drain Fly Control

If a black worm infestation has happened before, and you’ve tried everything to get rid of it and thought it went away but instead came back, chances are that you didn’t fully get rid of the infestation. Drain flies and black worms are stubborn insects, so they can withstand the effect of most pesticides or insecticides and thus survive to multiply again. 

Infestation Around Other Sites

If there are other areas around your bathroom or kitchen that may have been infested but not taken care of, the infestation can spread to the sinks. If there are areas in your bathroom with standing water that the drain flies can use to procreate and produce black worms, then they might spread to the sink drains as well. 

Sewer Line Breaks and Damages

In rare cases, the sink drains can get infested because of a line or break in a sewer line that’s connected to the sink drain. This opens a passageway for the drain flies and black worms to enter the sink drains and pipes and make it their habitat, resulting in a bigger infestation, according to Colonial Pest. 

How Do I Get Rid of Black Worms in My Sink?

Clean the Drain Filters

To get rid of the breeding grounds in the drain filters, clean them thoroughly by unclogging them and getting rid of all the organic matter that could become their breeding ground and nutrition. Make sure to clean them regularly and remove all the grime, hair, or any other clogged matter.

Use Bio-Enzymatic Drain Cleaners

Enzyme-based cleaners eat through the organic matter stuck in the pipe filters and drains, destroying the worms’ habitats. These cleaners also soften up the grime, making it easier to be cleaned. Some examples of bio-enzymatic cleaners are Green Gobbler and Drano Max. 

Home-Remedies: Hot Water, Baking Soda, and Vinegar

Pouring hot water down the drain not only softens up the matter stuck at the sides of the pipes but also kills the insects directly. Pouring baking soda not only kills the worms but also breaks down the sludge and makes it easier to clean up. White vinegar works in the same way; just let it sit inside the drain for a few seconds. 

Clean the Pipes With a Pipe Brush

A pipe brush is better for getting off all the matter stuck to the sides of the pipes, cleaning them efficiently. Move the tool up and down to properly clean the whole pipe, and of course, to remove all of the drain flies and black worm habitats or breeding grounds. 

Use Plumbing Snakes and Plungers

This tool is useful for getting rid of the organic matter and dirt present deep down the drain pipes. Insert the coil into the pipe and twist it through in order to properly destroy the breeding grounds and get rid of all the sludge. Alternatively, you can also use a plunger. 

Clean the Surface Near the Sinks

Sometimes flies may lay eggs on the surfaces near the sinks, so it’s better to clean them with bleach to kill the larvae and any hiding worms. The chemical substances present in the bleach are poisonous to the larvae and the worms, killing them effectively. 

Call an Exterminator and Plumber

For proper cleaning, call an exterminator. The experts know how to deal with an infestation and how to make sure it doesn’t happen again. If the infestation is due to a sewer break, call in a plumber to find out the problem and fix the break before the infestation grows. 

How Do I Prevent Black Worms in My Sink?

Kill the Adult Drain Flies

Adult drain flies are the biggest cause of the multiplying numbers of black worms. Even if you kill all the black worms, the flies will just keep on procreating, producing more larvae, and the infestation will keep on persisting. Use fly traps, swatters, or spray insecticides to get rid of the drain flies once and for all. 

Home-Remedies to Prevent Infestation

If there’s a sink that you don’t use and still want to prevent an infestation in it, we recommend using mineral oil. Covering the surface of the drains with the oil will repel all the adult flies laying eggs on the surface and help get rid of the present worms, according to Den Garden. 

Insect Growth Regulator

These regulators stop the worms and the larvae from becoming drain flies as a process of their evolution, and thus they die immediately. This makes sure there are fewer transitioning adult flies to lay more eggs and produce more black worms. 

Use an Effective Insecticide

Try using an organic insecticide and apply it down the drains and pipes. What this will do is repel the drain flies and kill all the present black worms residing in their habitats. 

Remove Standing Water and Moisture

Standing water and moisture become the biggest breeding ground for drain flies. Reduce moisture buildup in and around your sinks by doing a routine check and using it from time to time to get rid of any buildup. 

Regular Cleaning and Maintenance

Use the home remedies and chemical fixes mentioned above to clean your drains and unclog them from time to time. Keeping your sinks clean regularly is the most efficient way of preventing an infestation in the future. 


Black worms are larvae of drain flies that survive in damp and dirty environments and feed off of organic matter. These larvae later turn into adult flies which can procreate to make more black worms. Irregular cleaning of the sink drains, pipe breakage, standing water, decaying organic matter, and the presence of other infested sites can be the reasons for black worms appearing in your sink. To deal with this problem, you can use chemical-based remedies, contact the experts, do routine cleaning, or use home-based remedies. We recommend getting rid of adult flies, using growth regulators, and removing infested sites and standing moisture to prevent another infestation.

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