There is nothing quite as annoying as stepping into your pristine bathroom in the morning only to see a dozen tiny, fuzzy flies lazily hovering around your sink or shower. If you’ve tried swatting them only to find more the next day, you aren’t alone. In Reading, many homeowners struggle with these persistent pests—especially in older properties or houses with less-frequent drainage use.
At Reading Pest Controllers, we know that these “fuzzy little squatters” are more than just a nuisance; they are a sign that something is hiding in your pipes. We’ve put together this guide to help you understand what are drain flies, whether they pose a risk to your family, and, most importantly, how to get rid of drain flies for good.
What Are Drain Flies?
If you are seeing tiny insects that look like miniature moths, you are likely looking at Psychodidae, commonly known as drain flies (or sewer flies).
How to Identify Them
- Appearance: They have short, fuzzy bodies and large, round wings that make them look like tiny moths.
- Size: Usually very small, between 2mm and 5mm.
- Behaviour: They are poor fliers. You’ll mostly see them crawling on walls near drains or making short, hopping flights.
- Habitat: They lay their eggs in the “biofilm”—that thick, gelatinous slime that builds up inside pipes, sewage drains, and septic tanks.
Do Drain Flies Bite? Are They Harmful?
One of the first things our clients ask is: “Do drain flies bite?”
The short answer is no. Drain flies do not have the mouthparts to bite or sting humans. Unlike mosquitoes or midges, they aren’t interested in your blood.
However, while they don’t bite, the question of “Are drain flies harmful?” has a slightly more complex answer. Because they live and breed in sewage and organic slime, they can mechanically carry bacteria from the drains onto your surfaces. While they aren’t considered a major disease vector, you certainly don’t want them landing on your toothbrush or kitchen counters.
Fruit Flies vs. Drain Flies: Which One Is It?
It is very easy to confuse these two. However, the treatment for one won’t necessarily work for the other.
| Feature | Drain Flies | Fruit Flies |
| Appearance | Fuzzy, moth-like, dark grey/black | Smooth, tiny, tan/yellow with red eyes |
| Primary Food | Organic slime in pipes | Overripe fruit, fermenting liquids |
| Flight Pattern | Short, “jumpy” flights | Fast, hovering near food |
| Location | Drain flies in bathroom or laundry rooms | Kitchens and near bins |
If you think you might actually be dealing with fruit flies, check out our other insect control page for more specific identification tips.
How to Treat Drain Flies: Finding the Source
To understand how to treat drain flies, you have to stop thinking about the flies you see and start thinking about the slime you don’t see. Killing the adults is like trying to empty the ocean with a teaspoon—as long as that slime exists in your drain, new flies will hatch every 48 hours.
The Tape Test
If you aren’t sure which drain is the problem, try this:
- Dry the area around your sink and floor drains.
- Place a piece of clear sticky tape over the drain opening (sticky side down), but don’t cover it completely (leave some airflow).
- Leave it overnight.
- If you find flies stuck to the tape in the morning, you’ve found their “front door.”
How to Kill Drain Flies and Clear the Pipes
Many people think pouring boiling water or bleach down the drain is the answer. Candidly, it rarely works. Bleach flows past the slime too quickly to kill the larvae deep inside, and boiling water loses its heat before it can penetrate the biofilm.
1. Manual Scrubbing
If you can reach the area (like the drain cover or the top of the pipe), use a stiff pipe brush to physically scrub away the slime. This is the most effective way to destroy their breeding ground.
2. Enzyme or Bio-Cleaners
This is the best drain flies treatment. These cleaners contain specialized bacteria that “eat” the organic matter in your pipes. Unlike harsh chemicals, they coat the pipe and break down the biofilm over several days.
3. Fly Traps for Drain Flies
While you work on the pipes, you can use fly traps for drain flies to manage the adults.
- Light Traps: UV light traps are very effective at catching the adults at night.
- Vinegar Traps: A bowl of apple cider vinegar with a drop of dish soap can attract them, though it works better for fruit flies than drain flies.
Professional Drain Fly Solutions in Reading
Sometimes, the infestation is deeper than a bottle of cleaner can reach. If you have drain flies in the bathroom that won’t go away, it could indicate a cracked pipe under your floorboards or a deeper blockage in the main sewage line.
At Reading Pest Controllers, we don’t just spray the flies. We investigate the root cause.
- We use professional-grade foam treatments that expand to fill the entire diameter of the pipe, ensuring no larvae survive.
- We can identify if a plumbing leak is creating a damp breeding ground behind your walls.
- We provide long-term prevention advice tailored to Reading’s specific water and drainage systems.
If you are tired of sharing your shower with these fuzzy pests, we are here to help. You can read more about our approach on our blog or see our full range of services.
FAQs
Why do I have drain flies in a room I rarely use?
When a sink or shower isn’t used, the “P-trap” (the U-shaped pipe) dries out. This removes the water barrier that usually stops sewer gases and flies from coming up the pipes. If you have a guest bathroom, make sure to run the water for a minute once a week.
Can drain flies live in the kitchen?
Yes. While they love the bathroom, any drain with organic buildup—like a kitchen sink with a food disposal unit—can become a breeding ground.
Is it safe to use chemical drain cleaners every day?
We don’t recommend it. Harsh chemicals can damage your pipes over time, especially in older Reading properties. Enzyme-based cleaners are much safer and more effective for long-term control.
How long does it take to get rid of them?
Once the “muck” in the drain is gone, the remaining adults will die off in about 3 to 5 days. If you still see them after a week of cleaning, you likely missed a breeding spot.
Are they active all year?
In the UK, they are most common in the warmer months, but because our homes are centrally heated, they can breed year-round if the drains stay warm and slimy.
Do drain flies come from the toilet? for a garden wedding?
It’s possible, but less common than sinks or floor drains. If they are coming from the toilet, it usually means there is a seal issue at the base or a problem with the wax ring.