Why are there flies in my drain?
Small, fuzzy, moth-like flies resting on the bathroom wall or hovering around the shower, sink or floor waste are usually drain flies. They lay their eggs in the slimy build-up inside drains, and the larvae feed on it. Getting rid of them means getting rid of what they're living in. Sometimes that's simple cleaning; sometimes it's a sign of a blocked or broken pipe that keeps feeding them.
Where they come from
Build-up in the drain
Hair, soap scum, food and grease coat the inside of pipes and traps. That film is exactly where drain flies breed.
Rarely used drains
A guest shower, a laundry tub or a floor waste that dries out gives flies an easy way in and a quiet place to breed.
Slow or blocked drains
Water and waste that sit in a slow pipe give flies more of what they need.
Broken pipe under the floor
If flies keep coming back after cleaning, a cracked or broken sewer pipe under the house or slab can be leaking waste into the ground, where they breed out of reach.
What you can do
- Remove and clean the grates and the top of the trap, and scrub away the slime you can reach.
- Pour hot (not boiling) water down rarely used drains every week or two to keep the trap full.
- Avoid harsh chemical cleaners. They rarely reach the build-up properly and can damage pipes.
- Tape a piece of clear plastic over a drain overnight. Flies stuck to it the next morning tell you which drain they're coming from.
When to call a plumber
If the flies keep coming back, the drain is slow, or there's a smell, there's usually more going on. We clean the pipes properly with a high-pressure jetter, which strips out the build-up flies breed in, and use a camera to check for broken pipes or sagging sections holding waste. You get clear options and a fixed price before any work starts. See drain jetting and CCTV drain inspection.
In southern Eastern Suburbs homes
Older homes in Matraville, Botany and Kingsford often have cracked clay pipes under suspended timber floors. When drain flies keep appearing in a bathroom no matter how often it's cleaned, a broken pipe under the floor is something we check for.
Why locals call us
- Local to Matraville and the southern Eastern Suburbs
- Free on-site quotes, with a fixed price before any work starts
- Lifetime labour warranty on our workmanship
- 100+ five-star Google reviews
- Licensed plumbers and gasfitters (Lic. 398171C)
Common questions
What are the small flies coming out of my drain?
Usually drain flies, also called moth flies. They breed in the slimy build-up inside drains and traps.
How do I get rid of drain flies for good?
Clean out the build-up they breed in, keep traps full of water, and fix any slow or broken pipes. A professional drain clean removes the film from the whole pipe.
Are drain flies a sign of a plumbing problem?
Not always, but if they keep returning after cleaning, there may be a slow drain or a broken pipe holding waste.
Why are there flies in a drain I never use?
The water in the trap has probably dried out, giving flies a way in. Run water down it regularly.
Related help: drain jetting, CCTV drain inspection, blocked drains, water in the floor waste and gurgling drains. Local pages: blocked drains Matraville, blocked drains Botany, blocked drains Kingsford and blocked drains Kensington.