Little Flies by the Sink?
Those are drain flies, and they are breeding in the drain rather than flying in from outside. Take away the film they breed in and there is nothing left to hatch.
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If you're seeing small, fuzzy, moth-like flies hovering around your bathroom sink, shower drain, or kitchen, you're probably dealing with drain flies. They're also called moth flies, sewer flies, or filter flies. Whatever you call them, the fix is the same: find where they're breeding and remove it.
Why They Keep Coming Back
Drain flies don't come up from the municipal sewer system, despite the nickname. They breed inside your own plumbing, in the layer of organic buildup, sometimes called biofilm, that forms on the inside walls of a drain pipe over time. That layer is made up of soap scum, hair, grease, and food residue. In a drain that isn't used often, a guest bathroom, a floor drain, a rarely used shower, it can sit undisturbed for weeks, giving flies exactly what they need to lay eggs and thrive.
The larvae live inside that same film and feed directly on it. They don't feed on anything else in your home, and they don't travel far from the drain that produced them. That's useful to know: if you're seeing drain flies concentrated in one spot, the breeding site is almost always that exact drain, not somewhere else in the house.
The larvae mature within the film over roughly one to two weeks before emerging as adults. Adults are short-lived, but as long as the film is intact, new eggs keep replacing them, which is why an infestation can look constant even though individual flies don't live long.
The Treatment Schedule
Earthworm® Drain Cleaner does not kill drain flies, and we want to be direct about that: it isn't labeled or sold as an insecticide. What it does is remove what the flies and their larvae depend on. The formula introduces live, enzyme-producing bacteria that travel down into the drain and colonize the pipe walls, where they continuously digest the organic material that makes up the biofilm. As that film breaks down, the flies lose both their food source and the surface they lay eggs in.
- Find the right drainCheck every drain in the affected room, including floor drains and rarely used showers. Drain flies favor drains with slow flow or infrequent use.
- Clear what you can reachA drain brush or a bent wire pulls out hair and larger buildup near the opening. It won't reach the film coating the pipe walls further down, which is the part that matters.
- Pour it in at nightPour Earthworm® Drain Cleaner directly into the affected drain and let it sit, ideally overnight, so the bacteria have time to establish before water runs through again.
- Weekly for two to three weeksThat works through the existing buildup rather than just the surface of it.
- Then monthly, to keep it goneA monthly maintenance dose keeps the film from re-forming, which is what keeps the flies from coming back.
It's a slower approach than a spray, and it won't clear a room of flies in an afternoon. But it addresses the reason the flies are there in the first place, which is why it holds up over time in a way that killing visible adults doesn't.
Why Sprays Disappoint
Aerosol drain fly sprays and foggers are built to kill adult flies on contact, and they do that part effectively. What they don't do is reach the organic film where the next generation is developing. Treat the visible flies today, and if the film underneath is untouched, you'll likely see new adults again within a week or two, because the breeding site was never addressed.
That's the core issue with any adult-only approach: it treats the flies you can see and leaves the source alone.
When to Call a Plumber
Most drain fly problems resolve with consistent treatment of the organic buildup. If flies keep appearing after several weeks of regular treatment, or if you're also noticing sewage odors, gurgling, or standing water, there may be a cracked pipe, a dry P-trap, or another plumbing issue feeding the problem alongside, or instead of, buildup. That's worth a plumber's look rather than more product.
Not sure what you're looking at?
Drain flies are small flies in the family Psychodidae, usually about an eighth of an inch long, with a fuzzy, tan to gray body and wings that fold flat like a tiny moth's when at rest. They're weak fliers, so you'll typically find them resting on walls or tile near a drain rather than buzzing actively around a room. They don't bite and aren't known to spread disease to people. The problem they cause is presence and persistence.
Phorid flies (family Phoridae) are a separate species, sometimes called humpbacked flies for the way their thorax arches, or scuttle flies for their habit of running erratically across a surface instead of flying away. They're a similar size and color, which is why the two get mixed up so often.
The practical difference: drain flies breed almost exclusively in the organic film that lines older or infrequently used drains, while phorid flies will breed in a wider range of decaying organic matter, including drains, garbage disposals, and rotting produce. Either way, the treatment schedule above applies, since both breed in the same kind of buildup.
Take the breeding site away and there's nothing left to hatch. The 64 oz bottle covers the full schedule: weekly through the first few weeks, then monthly maintenance.
What we can tell you about our drain cleaner
- 4.85 out of 5, from 20 reviews
- Verified buyers of this product, not a curated selection.
- Free shipping, no minimum
- Every order to the continental US. No code, no threshold.
- Septic safe
- It adds to a septic system's bacteria rather than killing them off.
- Safe for the pipe itself
- No caustic reaction, no pH spike, no heat. Cast iron, copper, PVC and ABS.
- Made in the USA, never tested on animals
- Family owned and women owned.
- Fragrance-free option
- This bottle is Fresh Citrus and Sage. There is a fragrance-free version of the same formula.
