How to Get Rid of Drain Flies

Bugs are just an occasional way of life here in California. While most of the time you can control the problem with a visit from your friendly neighborhood pest control technician, there are occasional circumstances when the insects you’re finding inside your home are caused by a specific issue.

If you’re noticing small black flies in the bathroom, these might be drain flies.

Also referred to as sewer gnats, these annoying little bugs are usually harmless, but they can be an indicator of a much bigger problem with standing water and drain clogs.

Understanding how to identify these critters and learning what causes them is a big step in ensuring you don’t have to deal with them for very long.

Plus, it is important to know the bigger plumbing issue you might be dealing with if they randomly show up without warning.

Here’s what you need to know about how to get rid of drain flies.

a drain fly

What Is a Drain Fly?

Drain flies are tiny little flies that are usually apparent in kitchen and bathroom sinks and shower drains.

Like larger house flies, they have six legs, a pair of wings, and antennae. While many people think of them as being black, they are actually a gray color with little hairs all over their bodies, which gives them a sort of fuzzy look.

However, to see a lot of these details, you would need a microscope, as they are super tiny to the naked eye. At most, drain flies are 4 to 10 millimeters in length as adults.

Generally, these insects gather and mate in spots that have standing water. They feed off organic material that collects in the pipeline and gets stuck, which can be anything from hair in a shower drain or leftover vegetable peels in your kitchen garbage disposal.

They typically lay eggs in the area that is clogged, which leads to larvae hatching and living down in your disposal.

As they mature, the flies will leave the drain in search of more food. The life cycle of the drain fly is very short.

What Causes Drain Flies?

The cause of drain flies can really vary from one household to another. In most instances, the presence of sewer gnats is caused by a slow or clogged drain.

When the pipe collects with debris, droplets of water and that organic material they like to feast on, it gives them the perfect environment to live and breed.

Usually, you’ll notice them coming from drains that don’t get a heavy amount of use, for example, a guest bathroom shower that only gets used every few weeks.

Or it can even be your master bathroom drain, if there’s only one person in the household and the plumbing isn’t used more than once or twice per day.

The main takeaway here is that if you see drain flies, you have a clog somewhere in your plumbing system.

Although it might be minor, it is usually worth inspecting at a bare minimum to determine if the drain is running slow or that there are other indicators. If there’s a draining problem, it’s probably time to call in a trusted plumbing company to inspect the issue.

How Long Does It Take to Get Rid of Drain Flies?

The process of getting rid of drain flies is generally pretty simple.

Usually, boiling water or baking soda and vinegar are enough to flush out their nest and send them on their way.

If you have drain flies in your kitchen and keep organic ingredients like a bowl of fruit out on the countertop, you may want to toss those items as they are likely contaminated. After a couple days, your home should be free of annoying gnats.

However, your efforts could be moot if you’re not addressing the bigger issue of the slow or clogged drain they’re living in.

If you still notice them coming back after going to all of the effort to kill them off, it is likely that a new colony has moved back into your plumbing system.

That’s when it is definitely time to tackle the clog issue and remove their ideal habitat to keep flies from coming back for good.

can bleach to kill drain flies

Will Bleach Kill Drain Flies?

One common remedy for killing drain flies is using household bleach. This is a very useful and cost-effective manner for getting rid of these little pests with an item you already have around the house.

A cup of household bleach is generally more than sufficient to kill most drain flies, and all you need to do is pour it down the affected drain. The chemical is strong enough to kill the larvae, and the rest of the adult flies should die off within a few hours to a day or so.

Always be very careful when handling bleach and wear protective gloves to avoid skin burns in case of spills.

Bleach is not recommended if you have a septic system. The bacterial environment of your septic tank is very fragile. If you use too much bleach, you could kill the microbes living in your tank. Instead, opt for something a little gentler.

baking soda and vinegar

A safer alternative to using bleach is combining 1/2 cup of salt with 1/2 cup of baking soda and 1 cup of white vinegar.

Pour the mixture down the drain, let it set overnight, and pour boiling water over it the next morning. This is also much better for your plumbing than using bleach.

boiling water to kill drain flies

Will Drain Flies Go Away?

Yes, drain flies eventually go away if you’re taking steps both to kill the existing ones and ensure the spot they’re coming from is handled.

If you’re using the methods we described above and still see flies after a few days, you might have multiple spots in your sewer pipe where they’re breeding or it could be a different species of gnat altogether.

Fruit flies are related to drain gnats and often look the same. If you think you have sewer flies in your kitchen but can’t seem to get rid of them, look around to make sure there aren’t other culprits drawing in insects.

For example, wine corks with a bit of liquid on them, old bottles, or even a piece of fruit long forgotten by your family can easily become the ideal breeding spot for many different types of bugs to inhabit your home.

Let Us Help With Your Drain Clog Problems

If you’ve tried to figure out how to get rid of drain flies and are still having issues, it might be time to call in the professionals for help.

At RT Olson Plumbing, we’re here to assist with any slow, partial or major drain clog issues you’re experiencing.

By fixing the source issue, you can prevent sewer flies from having a place to live and breed, thus eliminating the overall bug problem. Contact us today to schedule an appointment.

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Owner - Operator at RT Olson Plumbing
Bob Olson has over 18 years experience in all aspects of residential and commercial plumbing. He's a 4th generation plumber. With over 400 five-star customer reviews, he runs one of the best-rated plumbing companies in Riverside, CA.
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