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The tiny flies hovering around your toilet, sink, or floor trap? They are usually drain flies.
Also known as moth flies or sewer flies, they breed in damp drains filled with organic buildup. While harmless, they multiply quickly when the source is left untreated.
Malaysia's humid weather makes bathrooms more prone to moisture buildup, so occasional drain fly problems are fairly common even in clean homes.
Drain flies are attracted to slime and residue inside pipes
Drain flies lay eggs in the thin layer of grime that forms inside drains and pipes. Their larvae feed on organic matter such as soap residue, hair, mould, bacteria buildup, and waste sludge.
Bathrooms with poor ventilation, standing water, or rarely cleaned floor traps are more likely to attract them.
Common breeding spots include:
- Floor traps beside the toilet
- Sink drains
- Shower drains
- Overflow holes
- Areas with hidden leaks
If you are unsure where the flies are coming from, use clear tape to test the drains
Place tape loosely over suspected drains before sleeping, with the sticky side facing down. Leave a small gap for airflow. If flies stick to the tape the next morning, that drain is likely the breeding source.
This helps narrow down which area needs cleaning instead of treating the whole bathroom blindly.
Once you've identified the source, cleaning the drain thoroughly is the most effective solution
Killing the adult flies alone will not solve the problem because larvae inside the drain will continue hatching.
To clean the drain:
- Pour boiling water into the drain
- Add baking soda followed by vinegar
- Leave it for 15 to 30 minutes
- Scrub the inside of the drain using a long brush
- Flush again with hot water
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The scrubbing step is important because drain fly larvae cling to the slime layer inside pipes.
NOTE: If your shower drain is the cause, you'll want to make sure you clear the drain of any hair or organic buildup first. Remove shower drain traps (or waste traps) and make sure the entire drain is clear.
Persistent drain flies may point to plumbing problems
If the flies return after repeated cleaning, there may be an underlying moisture issue.
Possible causes include leaking toilet seals, cracked pipes, standing water under tiles, dry floor traps, or poor bathroom ventilation.
Unused bathrooms are especially prone to drain flies because water in the trap can evaporate over time, allowing insects to enter through the pipe system.
After clearing the infestation, basic bathroom maintenance usually keeps the problem under control
Drain flies are mainly a sanitation and moisture issue. Once the breeding source is cleaned properly, the infestation usually reduces quickly.
To prevent drain flies, remember to clean bathroom drains weekly and remove hair and debris from floor traps.
