How to get rid of drain (sewer) flies

Featured image: Wikipedia

What are drain flies?

Drain flies (Psychodomorpha) are not the only flies that can infest drains so it is important to be able to identify which type of fly you have as the treatment to eliminate them may vary.

an adult drain fly

What do drain flies look like? Image source:

Drain flies are quite small, about 1/8” in length.  They may be either black or brown but the crucial feature that identifies them from other species is a unique vein pattern on the wings.  Their bodies are also covered with numerous fine hairs.  They can also be called moth flies, sewer flies, or filter flies.

The clue is in the name – they live and breed around drains, sewers, septic tanks, and any surrounding soil or earth that has become contaminated with sewage.

How do you know if you have drain flies?

The presence of drain flies may be quite obvious but not always. The flies live off the film of debris that sits on the drain sides and the organic matter within the drain.

If you want to check for drain flies then place some masking tape over the top of the drain with some holes in it to allow for the flow of air. Leave the tape in place for 48 hours.  If you find flies stuck on the tape then you have your proof.

You may also see drain flies on the walls and ceiling near a suspect sink particularly if it is not used very often.  A popular time to see them is when you return home after a holiday and the house has been empty for a couple of weeks.

where do drain flies breed

How to eliminate drain flies

Drain flies are very common in and around kitchen and bathroom drains; they don’t bite but most people consider them unwelcome guests.  In small quantities, drain flies can actually be beneficial as they break down decomposing matter in the drains but they can quickly spiral out of control with new batches hatching every two to three days.

A lot of people don’t want to resort to harsh chemical products and solutions which you can quickly tip down the drain and forget about – toxic for the flies, too toxic for the environment.   But there are other methods to eliminate drain flies without using bleach or harsh chemical-based drain cleaners and these include:

  • Take a metal pipe brush and work it back and forth through the pipe against the sides followed by lots of boiling water to flush away what you have loosened
  • Divert flies away from the offending drain or sink outlet by creating a sugar trap. Equal parts of sugar, water, and white vinegar with around 10 drops of liquid soap in a bowl by the sink.  The flies will be attracted to the fragrance and drown in the liquid
  • An alternative is a vinegar trap that you can make with ¼ cup of apple cider vinegar poured into a glass. Cover with saran wrap and poke holes through the plastic with a knife or pen.  Leave the glass by the sink, the flies will be attracted to the cider vinegar and once inside the glass will drown
  • Flush the drain with boiling water twice a day for a week
  • Mix half a cup of salt and half a cup of baking soda with one cup of vinegar, pour it down the drain in the evening, and allow it to sit there overnight. Flush the drain with boiling water in the morning
Green Gobbler Drain Clog Dissolver

Get rid of sewer flies by removing their home – Green Gobbler unclogs drains and can liquefy hair within minutes. It’s safe to use in pipes, toilets, sinks, tubs, and showers.

Prevention is better than cure

Good management is the key to keeping drain flies at bay.  Pour half a cup of baking soda in the drain weekly and then flush through with lots of hot water.  Or, pour half a cup of white vinegar into the drain, allow to sit for thirty minutes, and then flush through with warm or hot water.

If the drain smells then this doesn’t necessarily mean you have or will get drain flies.  Odor can be controlled with the juice of half a fresh lemon just poured into the drain.

Many people worry that drain flies are an indicator of dirty drains or an unclean home but this is not usually the case.  Drain flies are optimistic and will target clean as well as dirty drains.  Drain flies do not bite or transmit any disease to humans, they are just unwelcome guests because when they congregate in large numbers, they are carrying minute particles of matter from the drains where they live – not something you want to be transferred into your home.  So they could contaminate foodstuffs – enough said.

Removing unwanted insects or other forms of pests does not have to be done in a way that is harmful to the environment.  So just stop and think before you reach for that drain cleaner – there are other ways.

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