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Drain Fly Infestation

Filter/Drain Fly Control Services

Call your London Fly Exterminators on 0203 600 0351

filter/drain flies


These small hairy flies can invade buildings in swarms. Their small size allows them to gain access into various types of premises, the main type being sewage treatment plants. These flies in swarms will actually be a welcome sight around sewage works and filter beds as they assist in the breaking down of the sludge waste matter into tiny faecal pellets.

Size, Shape and Colour

These flies are little more than 2mm, they are easily recognised by their hairy wings and numerous veins. Some species have patterned wings, however the wings are usually held roofwise over the body at rest, some rest with their wings partly spread. The colour of these flies in adult form is grey.


The eggs will be laid in preferred environment being wet and rotting, such as drains and slow moving gullies where there may have been a back up of slurry. Approximately 200 eggs willbe laid in batches. The larvae will actually live and feed within the decaying matter right up until pupation. The eggs will hatch within 7 days but take as little as 1 day if the conditions are suitable. It will take anything from 10-50 days for the larvae to develop to adulthood. The larvae will reach a size of 9mm prior to the adulthood development. These small flies, during the right conditions and environment can provide up to 8 bred generations a year.

Preferred Foods

Ideal food sources for these small flies is fungal and bacterial matter, algae, decaying and wet matter in drains and gullies.


Sewage works, filter beds, drains, gullies, sometimes around toilets and sanitary bins. During the summer months they become a nuisance when alighting on builds which are of close proximity to sewage works or filter beds.

Pest control treatment for filter/drain flies - Call 0203 600 0351

As with most of our pest control treatments, we usually do two visits as a follow up visit allows us to make sure any actions we take are successful. Our fully trained pest control technician starts by talking to you about the problems you are having before assessing the situation.  Please be aware that the pest controller will often need to inspect other areas and not just the visible source.

Residual insecticides, usually sprays and dusts are the normal treatment for Filter/Drain Flies. In houses we normally need to treat the kitchen and the garden areas where the flies may have originally found their way in.

As with all our treatments, the pest control technician will leave a report with you with details of any treatments and recommendations.  If a follow up visit is likely to be needed, our technician will arrange a suitable date and time with you. Generally this will be about a week or two later and sometimes a second treatment is required.
We are a leading pest control company working in and around the Hertfordshire area, using the latest techniques to ensure your pest problems are completely eradicated.
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