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Drain flies, also known as moth flies or sewer flies, are a common household nuisance, especially in bathrooms, kitchens, and laundry areas. While they’re not harmful, they can multiply quickly and usually indicate a deeper issue inside your drains.
If you’re wondering how to get rid of drain flies for good, this guide explains what causes them, which DIY methods actually work, and when professional plumbing is needed to stop them permanently.
Drain flies are small, fuzzy insects that thrive in damp environments. Unlike fruit flies, they don’t come from food left out on benches; they breed in organic buildup inside drains, floor wastes, and pipes.
They’re often a sign of:
Killing the flies alone won’t solve the problem unless the source is removed.
Drain flies are usually linked to one or more of the following issues:
In older Australian suburbs, clay pipes and mature trees can make drain fly issues more frequent.
If the infestation is minor, you may be able to reduce drain flies with the following DIY steps. These work best when the drain is slow but not fully blocked.
Use a stiff drain brush to scrub the inside of the drain opening and remove visible sludge. This is the most important step — surface cleaning alone is not enough.
Slowly pour boiling water down the drain in stages to help dissolve grease and organic residue. This can reduce breeding material.
Pour half a cup of baking soda into the drain, followed by half a cup of vinegar. Allow it to fizz for 15–20 minutes, then flush with hot water.
For soft blockages, plunging can help dislodge buildup further down the pipe.
⚠️ Avoid chemical drain cleaners. They can damage pipes and rarely remove the organic sludge that drain flies feed on.
Natural methods can help reduce fly activity, but they won’t fix deeper drainage problems.
These methods are best used alongside proper drain cleaning.
If drain flies keep returning, there’s usually an underlying plumbing issue.
You should contact a licensed plumber if:
Professional plumbers use CCTV drain inspections and high-pressure water jetting to remove organic buildup completely, something DIY methods can’t achieve.
Permanent removal requires eliminating the breeding source inside your pipes.
Long-term solutions may include:
Without fixing the underlying cause, drain flies will keep returning.
Once the problem is resolved, prevention is key.
Routine maintenance is far cheaper than emergency plumbing repairs. Maintaining clean drains and household hygiene is also recommended by NSW Health to reduce sanitation and pest risks.
Small flies near drains, slow drainage, gurgling noises, and unpleasant smells are common early indicators.
No, but they indicate unsanitary conditions inside your drainage system.
Vinegar can reduce adult flies, but it won’t remove the organic buildup causing the problem.
Yes. Drain flies often indicate partial blockages or stagnant water inside pipes.
If DIY methods don’t work or the problem keeps returning, professional plumbing is recommended.
If drain flies keep coming back, it’s often a sign of deeper pipe or drainage issues. Civic Plumbing provides professional drain cleaning, CCTV inspections, blocked drain services, and preventative maintenance across Sydney.
Call 0410 790 630 to book an inspection and stop drain flies at the source permanently.
