How to completely eliminate drain flies?

How to completely eliminate drain flies?

The key to eliminating drain flies is cleaning the larval breeding site — the sludge inside drainpipes. Simply killing the adults on the walls is useless; as long as larvae remain in the pipes, new adults will emerge in a couple of days.

Clean the drains — fundamental solution

Drain fly larvae live in the sludge in floor drains and pipes; they must be removed at the source:

• Open the floor drain cover and use an old toothbrush or brush to scrub the inner walls of the pipe.
• Disassemble the traps under sinks and washbasins to clean the sludge from the bends.
• After scrubbing, pour a pot of boiling water down the drain to kill any remaining eggs and larvae.
• Also check the sealant around the toilet base for damage.

Apply insecticide

After pipe cleaning, spray dinotefuran-containing household insecticide to kill adults on walls:

• Spray evenly on bathroom walls and corners.
• Focus on areas around floor drains, outer walls of drainpipes, and under the sink.
• Adults that land or crawl over the treated film die.
• Once dry, the insecticide forms an invisible film effective for 2-4 weeks.

Ongoing prevention

• Pour boiling water down the drain weekly to prevent larval re-establishment.
• Keep floor drains covered when not in use to prevent adults from emerging.
• Regularly check pipes for blockages; standing water is a breeding ground for drain flies.
• Keep the bathroom dry and well-ventilated; damp conditions favor their reproduction.

Treatment effectiveness

Following these steps will generally eliminate the problem within 1-2 weeks. Without treating the pipes, killing adults is futile — you will never be completely free of them.