4 Main Causes Of Drain Flies (& What Attracts Them)

If you’re dealing with drain flies in your home, then you may be wondering what’s causing them in the first place. Well, the truth is no matter where you find drain flies in your home, the causes behind why they’re there are always going to be the same.

In this article, you’re going to find out what’s causing drain flies, what they’re attracted to, and the most common areas they tend to inhabit! So keep reading to find out everything you want to know!

What Causes Drain Flies?

There are 4 main causes of drain flies. And knowing all the reasons can help you identify and look for other areas in your home where drain flies may be inhabiting. With that being said, here are the 4 main causes of drain flies in your home.


First of all, drain flies are going to be attracted to any areas that are damp or have standing water. Shallow dirty water is normally their go-to, and this can be found all around your home, both inside and out.

Standing water and stagnant water often house decaying organic material, which drain flies love to eat.

A Food Source

And of course, on the subject of eating, drain flies are going to thrive anywhere there’s a food source as well. One of the reasons they love drain pipes is because they’re often full of organic material they can eat, such as old food, soaps, and even hair.


Drain flies also love humidity. You should now be beginning to see why drain flies love the drains and pipes in your home so much. They provide everything they’ll need to thrive. Not only are they damp and full of food.

But any standing water in the pipes is going to create an incredibly humid environment where drain flies are going to thrive.

However, when you begin to think on a larger scale, you can understand how drain flies end up inhabiting entire rooms (such as your bathroom) when they aren’t aerated properly.


Although they’re more active at night, drain flies love light as well. Any light source is going to help them navigate, and just like moths, if they notice a light source, they’ll often fly directly towards it!

Macro Photography of Drain Fly Isolated on White Background

Why Are Drain Flies Attracted To This?

Drain flies are primarily interested in eating and breeding. So any area that is humid enough with plenty of standing water and build-up of organic matter is going to be the perfect place for both of these things to happen.

And the rate at which they’ll be able to lay eggs is astounding. Each drain fly can lay between 10-200 eggs which hatch in about two days, and then after another couple of weeks, they reach adulthood, where each adult can then produce another 10-200 eggs.

So as you can see, if you don’t deal with drain flies fast, they can get out of hand incredibly quickly.

What Areas Of Your Home Do Drain Flies Tend To Inhabit?

Now you know what’s causing drain flies, then you’re probably wondering where about in your home they may be inhabiting. Here are the most common places you can find them!

Drains & Pipes

This is an obvious one, but most of the time, you’re likely going to find drain flies as well as their larvae and eggs in drains and pipes.

It’s particularly common for drain flies to inhabit pipes that haven’t been used in a while, so make sure you’re flushing your drain and turning your shower on regularly.

Moist Compost

Another common place to find drain flies is in moist compost. Once again, this is an area where drain flies find everything they need to breed. So if you have a compost bin, make sure you’re covering it completely to stop drain flies from being attracted to it.

Septic Tanks

If there’s a crack in your septic tank or the seals have broken, then your septic tank could be the reason that drain flies have started flocking to your home.


As you can imagine, garbage is going to be a massive attraction to drain flies, so if possible, keep garbage away from your home or completely contained in your home.

Mops And Buckets

If you have left mops and buckets out, then this could be another area of standing water that is attracting drain flies.

Storm Drains

If it’s been raining a lot in your area recently, then the storm drains around you may be full of standing water which is attracting drain flies to your home.

What Do Drain Flies Look Like?

Now you know the causes and drain flies and places you’re likely to find them, it’s important to make sure that you know what they look like. Otherwise, you could be trying to rid of the wrong pests.

With that being said, drain flies tend to be about 1/8th of an inch in length. Their bodies look a lot plumper than other types of flies, and because of the fine hairs on their body, they can often look slightly furry.

They range in color from pale grey to black, and you’ll often find them sitting on vertical surfaces. If you try to shoo them away, you’ll also notice they don’t tend to fly far but instead almost hop from one location to another.

How To Know If You’re Dealing With Drain Flies

The easiest way to know if you’re dealing with drain flies or not is to put duct tape over the drains you think they’re coming from. Then, in the morning, check the duct tape. If you notice drain flies are stuck to it, then you’ve definitely got an infestation.


Here are some more frequently asked questions people have about drain flies.

How Long Do Drain Flies Live?

Once drain flies reach adulthood, they’ll only live for around 20 days before dying. But the rate at which they can reproduce, you’ll definitely want to make sure you’re getting rid of them as soon as possible.

Are Drain Flies Dangerous?

Fortunately, drain flies themselves aren’t dangerous; however, they are known to trigger asthma in some people. As well as this, you have to remember where they come from, so they’re not the most sanitary animals to leave in your home.


As you can see, understanding what causes drain flies to infest your home is the key to finding the different locations you can find them breeding in your home.

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