Domakihub How to Get Rid of Drain Flies for Good
Identify, treat, and prevent drain fly infestations in any home, rental, or hospitality property.
Reviewed by Domakihub home & decor pros · 2026-06-23 · 4 min read
Drain flies — also called moth flies or sewer gnats — are tiny, fuzzy-winged insects that breed inside the organic sludge lining slow or seldom-used drains. The video above walks through the core treatment methods; this article turns those methods into a step-by-step plan you can action today. Whether you manage a villa in Crete, an Airbnb in Athens, or a hotel bathroom on Santorini, a drain fly problem can be solved within one to two weeks without harsh chemicals.
What Are Drain Flies and Why Do They Appear?
Drain flies (Psychoda alternata) are 1–5 mm long and have a distinctive moth-like silhouette. They do not bite, but they are a hygiene red flag. Adults live only a few days, yet a single female can lay up to 300 eggs inside the gelatinous biofilm that coats the inner walls of drains, so populations explode quickly in warm weather — exactly the Mediterranean summer climate Greece experiences from May to October.
They are most common in bathrooms, kitchen sinks, floor drains, and any drain that sits unused for more than a week. In rental properties and hotels, the gap between guest stays is a prime breeding window: even a small amount of standing organic matter is enough.
How to Confirm You Have Drain Flies (Not Fruit Flies)
The simplest confirmation test is the sticky-tape method: place a piece of clear tape, sticky-side down, over the suspect drain and leave it overnight. If you peel it off the next morning and see small, fuzzy-winged insects stuck to it, you have drain flies. Fruit flies are rounder, reddish-brown, and hover near overripe produce — not drains.
Check every drain in the property, not just the obvious one. A secondary bathroom or a laundry floor drain that is rarely used is often the true breeding source, even when the insects are seen elsewhere in the building.
5 Steps to Eliminate Drain Flies
- 1
Confirm the infested drains with the tape test
Place a strip of clear tape sticky-side down over each drain opening before you go to sleep. Remove it after 8 hours. Any drains with adult flies stuck to the tape are active breeding sites. Mark all affected drains so you treat every one — missing even one drain will restart the infestation.
- 2
Mechanically clean the drain interior
Pour a kettle of near-boiling water slowly down each infested drain, then use a long-handled drain brush or a plumber's snake to scrub the inside walls of the pipe. Follow this immediately with a second pour of hot water to flush the loosened biofilm out. This physical removal is the single most important step: no product will be effective if the organic breeding layer remains intact.
- 3
Apply a biological drain gel or enzyme cleaner
After scrubbing, apply a biological drain cleaner — available at hardware stores (sklavos, Praktiker) or online — directly into the drain. These enzyme-based gels digest the remaining organic matter rather than simply masking it with bleach. Do not use bleach as a primary treatment: it briefly kills adult flies but does not remove the biofilm, so the population rebounds within days. Apply the gel every night for 5 to 7 consecutive nights.
- 4
Eliminate adults with an IGR spray or a DIY trap
To break the reproduction cycle above the drain, either apply a residual insecticide labelled for drain flies around the drain opening and nearby surfaces, or set a simple DIY trap: fill a small bowl with apple cider vinegar and a drop of dish soap, cover it with cling film, and poke a few holes in the top. Adult flies enter and cannot escape. Replace the trap daily. Reducing the adult population prevents new eggs from being laid while the drain treatment takes effect.
- 5
Prevent reinfestation by keeping drains active and covered
Once the infestation is clear, prevent a return by running water through every drain — including guest bathrooms, laundry drains, and floor drains — at least once a week when the property is between stays. Install silicone drain covers that allow water flow but block adult flies from entering. Schedule a monthly enzyme-cleaner treatment as routine maintenance, especially during the Greek summer when heat accelerates biofilm growth.
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FAQ
- How long does it take to fully get rid of drain flies?
- With consistent treatment — mechanical cleaning followed by nightly enzyme gel for one week — most infestations are eliminated in 7 to 14 days. The full lifecycle from egg to adult is 8 to 24 days, so you need to maintain treatment long enough to break the cycle completely and prevent any remaining eggs from hatching into a new generation.
- Will bleach kill drain flies?
- Bleach kills adult flies on contact but does almost nothing to remove the thick organic biofilm that lines drain walls, which is where eggs and larvae live. Because the breeding environment survives, the infestation returns within days. Enzyme-based biological drain cleaners are far more effective because they digest the biofilm itself.
- Can drain flies come back after treatment?
- Yes, if the root cause — organic build-up inside rarely used drains — is not addressed permanently. The best long-term prevention is a routine: flush every drain weekly, apply enzyme cleaner monthly, and use drain covers on seldom-used outlets. In rental and hotel properties, add a drain-check step to your between-guest cleaning checklist.