Fungus Gnats In Drains – What I Did To Get Rid of Them

Seeing tiny bugs come out of your drains can be quite annoying. 

They often seem to appear out of nowhere, but they can spread all over your house quite easily. Yes, they do not bite or do any visible harm, but they can be quite annoying. 

And besides, no one wants to keep growing gnats in their drain. So you are probably wondering – Is it hard to get rid of fungus gnats in drains? 

The short answer is NO. Gnats in drains are usually fairly easy to get rid of. You just need to know what you are doing. 

I was skeptical about the DIY advice for getting rid of gnats in drains because some of it seemed just way too easy. Is pouring boiling water in the drain really enough? Well, sometimes it is all you need, but not always. 

However, with the simple tips below, you’ll probably be able to get rid of gnats on your own. Here is what I learned from getting rid of persistent gnats in drains: 

Why Do Gnats Live In Drains? 

What are fungus gnats doing in your drains and why do they choose to live there? Well, drains are actually the perfect breeding places for multiple types of gnats. 

There is one thing we need to clear up first: it’s not the drains that actually attract gnats, it’s the filth inside the drains. What gnats love is decaying organic matter. If they can find it in your drain, that’s where they are going to stay. 

This is not to say that gnats live only in visibly filthy drains. Organic matter in the form of debris and slime can easily collect in the drains in areas that we never see. Hence, home owners are often not aware how filthy the inside of their drains is. 

Are You Sure It’s Fungus Gnats? 

If you are seeing gnats coming out of your drain, it’s quite possible that it’s actually not fungus gnats you are dealing with. 

The name ‘gnats’ is used for multiple species of insects which look and behave in a similar manner. These include fungus gnats, drain flies, fruit flies, and phorid flies, among others. 

The favorite habitat of fungus gnats is soil in pots around indoor plants. If the soil is kept too moist it creates the perfect environment or fungus gnats in combination with the warm indoor temperatures. 

Drain flies, on the other hand, breed in stagnant water. They are almost exclusively found in drains. Drains that are rarely used are their favorite spot. 

Fruit flies and phorid flies are attracted to rotting organic matter (especially fruit in case of fruit flies) which they often find in and around sinks and sometimes other drains. 

All of these gnats look very similar and behave almost in the same manner. The good news is that you don’t need to worry too much about identifying the type of gnat you are dealing with. The method for getting rid of them is always the same. 

How Did Gnats Get In My Drains? 

How did gnats get into your drains? And what’s attracting them to the drains in the first place? As I already mentioned, gnats love places that are warm and humid and they need decaying organic matter to feed on. 

Fruit flies, for example, prefer sugary substances like fruit, but that doesn’t mean they only live around fruit. Your kitchen sink could also be the perfect place for them if there are enough food particles hidden out of sight. 

Drain flies and phorid flies, on the other hand, specifically look for areas that are constantly moist. This is why they are the most common inhabitants of drains. 

How Many Gnats Could There Be In My Drain? 

Depending on the species, gnats can live from a couple of days up to a month. However, during a lifetime, a gnat can manage to lay hundreds of eggs. All it takes is one gnat finding the way to your drain and laying eggs there and you’ll quickly start noticing them in bigger numbers. 

Phorid flies, for example, rarely live longer than two weeks but during this time one fly can manage to lay 500 eggs. The data is not much different for other types of gnats. 

So what does that mean for your problem? Well, there might easily be hundreds of gnats in your drain. In fact, if you are seeing a couple of adult gnats flying around your house, there is high likelihood there are already hundreds of eggs and/or larvae somewhere in your home. 

Do I Need To Call An Exterminator To Get Rid of Fungus Gnats? 

So, there might be lots of gnats in your drain. But is that really a reason to panic? Not necessarily. In fact, there is really no need to call an exterminator to get rid of fungus gnats in drains in most cases. 

Gnats are actually quite easy to get rid of once you know where they are coming from. Below, you’ll find simple methods you can try out yourself. 

Of course, if the problem persists and you can’t seem to find the source, it might be best to call an exterminator. These cases are quite rare though! 

Getting Rid of Gnats In Drains: The Easy Way 

So how do we go about getting rid of gnats in drains? The first step will always be to determine where exactly the gnats are coming from. 

With gnats in drains, finding the source is usually not very difficult. You’ll usually notice a couple of tiny flies persistently flying around your drain. That’s probably the reason why you are here! 

However, to make sure which drain it is the gnats are living in, you might try the simple trick with sticky tape. 

As I mentioned before, gnats will choose your drain as their home if there is enough organic material (which could be just slime) for them to feed on. What you’ll want to do is basically clean out your drain so gnats don’t find it hospitable anymore. 

The Sticky Tape Trick 

For this method, all you will need is some transparent duct tape. Simply place it over the drain so it’s completely covered. What you want to do is seal the drain so the gnats can’t come out. Instead, they will get stuck on the tape. 

If you see gnats stuck to the tape, you’ll know this is the source you need to eliminate. 

While this will get rid of some of the gnats, this is not enough to get rid of them permanently. What you can catch this way are adult gnats, but their larvae can keep on growing inside the drain.

Cleaning Out The Drain 

In essence, this is what you need to do. Clean out your drain, any way you can. However, sometimes this is easier said than done. There can be debris stuck in the drain that is really hard to get rid of. 

For mild cases, pouring hot water down the drain might do the trick. Just bring a pot of water to a boil and pour it in there. This often helps when fruit flies start appearing around my sink. The method works best if repeated a couple of times over the course of a couple of days. 

However, drain flies can live in slimy films on the inside of your drain and water is not always enough. 

If it’s possible, also try cleaning out your drain with a flexible drain brush. If you want, you could also use some store-bought drain cleaners. Or, you could try the methods below with items you might already have around your home. 

Baking Soda And Vinegar 

This simple trick is a great way to clean your drains without extreme chemicals and kill the gnats in one shot. 

What you will need: 

  • ½ cup baking soda 
  • 1-2 cups vinegar 
  • A pot of boiling water 

To start, you’ll want to pour the baking soda inside the drain you are trying to treat. Next, take a cup of vinegar and pour it inside too. You can use apple cider vinegar or any other vinegar you have on hand – we just want something that is acidic enough. The acidity is what creates the reaction with baking soda which will cause the mixture to start fizzing and foaming. 

The foam might start coming out the drain. Do not worry, this is completely normal. In fact, it’s what we want to happen. 

Let the mixture sit in the drain for 30 minutes to 1 hour and then pour a pot of boiling water down that drain too to finish off the process. 

The natural reaction between baking soda and vinegar will do a great job at cleaning your drain. It will get rid of fruit flies and fungus gnats almost certainly. However, sometimes drain flies can be really persistent so you’ll have to repeat the process a couple of times. 


If the vinegar trick is not working and you’d like some heavier artillery, you might want to clean the drains with bleach. In fact, this is what many commercial establishments use to keep their drains clean and sterile. 

All you need to do is mix bleach and water in proportion of 1 to 10 (1 cup bleach and 10 cups water). Let the mixture sit in the pipes for about an hour and then flush it out with cold water. 

This method can also be used preventively to keep the gnats out of your drains. 

Gnat Traps 

Another thing you can do to fight gnats is create a simple trap. 

A gnat trap will probably not get rid of all of the gnats in your train. As we mentioned, the larvae and the eggs could be developing in there and you are only seeing adults outside the drain. 

However, the trap will allow you to quickly get rid of the annoying gnats or fruit flies flying around the drain. 

All you need to do is take a glass and fill it with some liquid that will attract the gnats. Vinegar, again seems to work well and so does wine. In general, gnats are attracted to sugary liquids. 

What you’ll want to do is cover the glass with plastic wrap or something similar and poke small holes on the surface.

The smell of vinegar, wine, or sugar will attract the gnats, but once they are in they will not be able to get out. 

Another method that I found works quite well is to skip the plastic wrap and instead create a mixture of vinegar, water, and sugar and then add a couple of drops of dish soap in there. 

The added dish soap will make the gnats drown in the water. 

Final Thoughts 

While dealing with a particularly persistent gnats in a drain situation, I have tried all of these methods. And I can tell you – they definitely do work. Thoroughly cleaning out your drains can be difficult sometimes, but this is all that you need to do to get rid of gnats in drains. 

To learn more about dealing with gnats in your household, check out some of these links: 

Black Flying Bugs In House Are NOT Fruit Flies – They Are…

I’ve Seen One Gnat Should I Be Worried?

Where Do Gnats Come from in my Bathroom – Key Facts To Know

Steve Foster

Mad about bugs and wanting to publish as many articles as I can to help educate people about these amazing beautiful creatures! For more info check out my about page

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