Drain flies: finding and removing the source

Published on September 28, 2026 — Speed 3D Services

Small flies come back near a shower or sink despite cleaning the room? The problem may be related to deposits in an evacuation, but the proximity of a siphon is not sufficient to prove it. We need to identify the insect and locate its place of development. Treatment of adults alone may leave the source in place.

Canalization, fruit or soil: not to be confused

The flies of drains, or psychodidids, have an appearance evoking a tiny butterfly. Larvae may develop in the wet organic matter deposited in the discharges. I'm not sure what I'm doing.University of California describes this link with organic drain film. Other small flies are associated with food or plants: they call for a different search.

Photograph an insect placed on a clear medium, then note the places where you observe it. While the activity is mainly concerned with fruit and waste, the guide Blows in the kitchen is more suitable. Here, the objective is to examine the evacuation and wetland tracks.

Prepare a map of the points to be checked

List sink, shower, floor siphons and equipment rarely used. Indicate the odours, slow discharges and leaks already known. In a restaurant, add the washing areas and accesses under the equipment, without disassemblying an installation to search for insects.

Note each check with its date. This method avoids cleaning the same point several times while forgetting a secondary evacuation. A general photograph also allows the professional to anticipate access and determine whether a plumber should intervene.

Clean the accessible source, not just surfaces

A superficial cleaning of the bathroom may leave the internal deposits accessible to larvae. Mechanical removal of organic matter in the accessible part of the drain is at the heart of the prevention described by the University of California. Follow the instructions for maintenance of the installation and involve a professional if access or winding is uncertain.

Do not improvise the mixture of the extractor, disinfectant and vinegar. Do not pour insecticide into an escape without explicitly intended use. If flow remains abnormal, look for the technical cause rather than repeat applications.

When to go from interview to diagnosis?

Ask for an inspection if insects persist, if several parts are affected, or if an inaccessible area appears to be involved. The application must specify what was cleaned and what could not be cleaned. In a collective building, report observations related to a common evacuation to the manager.

A useful diagnosis must answer three questions: which insect is present, where is the probable home, and what operations are involved in maintenance, plumbing or disinfecting? Clarifying these roles reduces the risk of paying for treatment that does not correct the source.

Request an intervention in the 06

Forward the photos, relevant documents and any recent work to our disinectation service. For a trade, indicate the closing times and restrictions on access to food preparation areas. The method will be determined after review, without promising an identical time frame for each facility.

Frequently asked questions

Do the flies prove that the sewer is broken?

No. Several sources are possible. A leak or a failure of evacuation is confirmed by a technical inspection, not by the presence of insects alone.

Does an adult trap solve the problem?

It can help to observe activity, but does not necessarily remove the material where the larvae develop.