Small fuzzy flies near a sink can breed in moist organic film. The drain may be the source, but a damp cabinet or a rarely used floor drain can also support them. Note where they collect before treating any one drain.
Check which fixture attracts them
After the fixture is idle, look for flies around the overflow opening as well as the drain. Compare nearby sinks and note any odor or slow flow. Clean accessible surfaces and repair visible moisture sources. Avoid mixing drain cleaners.
Report signs of a plumbing problem
If flies return along with slow drainage or an odor, tell the plumber which fixture is involved and whether it is used daily. A plumber can check for buildup or an issue with the trap. If flies persist after the plumbing is ruled out, a pest professional can identify the source.
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