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Small Black Worms In The Shower (What Are They And How To Get Rid Of Them)

drain fly larvae around shower drain

Small Black Worms In The Shower: Drain Fly Larvae

If you’re seeing small black worms wiggling around in and around the shower drain, you’re most likely looking at drain fly larvae. Within a few weeks, these little drain fly larvae will grow into adult drain flies.

And since drain flies can live up to three weeks, and new eggs can hatch every 48 hours, it’s important to get on top of controlling these little guys as soon as possible. 

Before I knew what drain flies were, I just simply noticed a tiny black moth looking creature in my shower. I’d turn the water on and he’d fly away. Then, I noticed two of them.  Then, I noticed 5.  Finally, I started to notice small black worms in the shower.

I started putting two and two together and that’s when I decided to take action and educate myself about these little black flying bugs and get rid of them once and for all. 

So, here’s what I learned and here’s what you can do if you happen to see little black worms in and around your shower drain.

What Are Drain Flies?

Also known as moth flies, sewer flies or filter flies, drain flies are small moth looking flies that are only about 1/8th of an inch in length. Most of to drain flies that I’ve seen have been black or very dark in color, but I’ve been told that they can also be more of a brown color as well.

Drain flies bodies are covered with a furry kind of hair and their antennae remind me of a narrow fern branch.

drain fly larvae look like little black worms in shower drain

Where Do Drain Flies Breed?

Drain flies love to congregate and breed in stagnant, shallow water and dirty drains. If this stagnant water is anywhere near a food source, bacteria and other organic matter which is also common in bathrooms, then you’ve found the perfect breeding grounds for drain flies, or moth flies.

Drain flies prefer areas that have been left untouched for a period of time, or are generally not used frequently. In my situation, they were coming from the jets of our jetted tub that we very seldom used.  

dirty stagnant shower drain is drain fly breeding ground

Other common places that drain flies will breed are in the P-traps of shower and sink drains, especially when those drains have not been used in a while and the water is just sitting stagnant in the P-trap.  

If you have a sink in your shop or basement which isn’t used very often, these are ideal breeding grounds for drain flies. These little flying bugs thrive on moisture and organic debris and can even pop up in a relatively clean areas around the house.

How To Tell If You Have Drain Flies

To know if you have drain flies or not is not always as easy as looking down at your shower drain and seeing tiny black worms. 

If you suspect you might have drain flies in your home or in your drain pipes, but aren’t quite sure, there are a few things you can do. Just follow these steps I learned about on

The Duct Tape Test

This is probably the best way to find out if you have adult flies in the drain and if it is a breeding site for them.

Simply cover your entire drain with duct tape and leave it overnight. Be sure to completely cover the drain. 

Drain flies, or moth flies, will try to come up out of the drain during the night and will get stuck on the duct tape as they exit the drain. 

This is a good test to check to see if you have drain flies because it not only tells you how bad the infestation is, but it also kills some of the flies while checking.

It’s recommended that you do the duct tape test several nights in a row to get an accurate idea of the infestation.

Check for Larvae

Drain flies like to lay eggs in the organic matter that builds up at the opening of your drain. According to This Old House, “Remove the drain cover, scrape some of the slime off the sides, and look for thin, tube-like, drain-fly larvae. If you don’t spot any here but are certain you have an infestation, this could be a sign that the eggs are being laid deeper within your pipes.”

How to Get Rid of Drain Flies

Now for the DIY pest control part. Here’s how to get rid of drain flies and those little worms crawling around your shower drain and drain pipes. Roto-Rooter recommends the following methods of killing drain flies and drain fly larvae.

Step 1: Make Sure Drain is Working Properly

Pour approximately 1/2 gallon of water down the drain where you see the drain flies or small black worms congregating. If the water drains away quickly, that means the drain is functioning properly. 

Step 2: Add Hot Water

Next, pour in a panful of very hot water to kill the drain fly larvae. IMPORTANT: Do not pour boiling water down the drain as it has the potential of cracking some materials.

Step 3: Add Vinegar OR Bleach

NOTE: Do not add both vinegar and bleach. Choose only one. Mixing the two together can create a toxic chlorine gas. 


Now pour one cup of white vinegar down the same drain. The white vinegar should kill any of the drain fly larvae stuck to the sides of the pipe. 


Pour one cap full of bleach down the drain. It doesn’t seem like much, but one cap full of bleach is all you need to kill any flies or larvae that are hiding in the drain pipe.

Read More: How To Get Rid of a Smelly Drain

Other Methods of Killing Drain Fly Larvae

In addition to using white vinegar or bleach, there are a few other household items you also use to kill drain flies and do your own pest control.

Salt, Baking Soda and White Vinegar

Pour in 1/2 cup of salt and 1/2 cup of baking soda plus a cup of white vinegar. Allow it to work its magic overnight then flush the drain with hot or boiling water the next morning. This will sanitize the drain and kill the flies, their eggs and the larvae.

How To Prevent a Drain Fly Infestation

It’s really not all that difficult to prevent a drain fly infestation. As a matter of fact, if you are actively using your sinks, showers and toilets, and water is continuously flowing through the drain pipes, then you’re probably not going to see an infestation.

However, if you plan on leaving the house for a few weeks or longer, or you think your environment is susceptible to drain worms, I would recommend doing the following in order to prevent an infestation:

Cover Unused Drains

Drains that are seldom used should be covered with a drain stopper or a flat rubber cover. These drain covers can be purchased on Amazon or at your local home improvement store.

Keep Drains Clean

You can prevent drain flies by making sure that you keep the drain pipes clean and free of soap scum and other drain line slime. Use drain cleaner gel once a week to keep organic matter from gathering on the sides of the drains. I recommend using drain cleaner at night when the drains will not be used for a few hours. This will allow the drain cleaner to work without being washed down the pipes and into the septic tank.

Read More: Does Shower Water Go Into Septic Tank?

NOTE: If you are on septic tank system, be sure to consult with a septic system pro before adding drain cleaners as they may harm the healthy bacteria in your septic tank.

If you choose not to use a drain cleaner, then you can keep the upper part of your drain clean and becoming a breeding area for little flies by using a metal pipe brush. Simply brush as much of the drain as possible, removing the gelatinous film from the sides of the drain pipes.

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