Drain flies not coming from drain? Drain flies, also known as sewer flies or filter flies, are so called since the flies regularly nest and lay their eggs in drains, sewage systems, and other damp areas. Drain flies, however, can exist in places where there is no nearby drain or sewage system, so do not be deceived by the name.

Some people think that drain flies come from the drains but this is not entirely the case. Your pipes or drains are not the only places where drain flies come from—they can come in from the outside and then are attracted to your drains.


Identify what attracts the drain flies to your home to make controlling them easier.

Drain flies not coming from drain

Drain flies not coming from drain

If you have no drain, it’s possible that the drain flies are coming from a different source. Moreover, drain flies usually come in from the outside when they smell the organic substance they need to breed, and not from your pipes or drains. They enter your apartment through small holes.


The drain flies you’re seeing are likely coming from a different area, such as a damp or moist region within or close to your home. You might encounter drain flies in a humid or moist place as they are attracted to dampness and frequently hang around near sources of standing water or moist organic particles.

You might want to try checking for other potential sources of moisture or standing water in or around your home if you have no drain nearby or any plumbing issues.

Meanwhile, drain flies are most active in the evenings when they hover about drains and sinks (see Drain Flies (Moth Flies) publication on the Ohio State University website. Other small flies that are commonly mistaken for drain flies include fruit flies and phorid flies found in kitchens and bathrooms.


Why can’t I get rid of drain flies?

Drain flies may be present due to a secondary infestation that went undetected and untreated in another location. Drain flies might be breeding in other bathroom drains, a floor drain, a laundry room drain, or a sump pump.

All of the tiny wet gunk gnats can spawn in a variety of places with ripe, decaying, or rotting semi-liquid organic materials in addition to drains. For instance, filthy potted plants, filthy trash cans or recycle bins, drip pans under appliances, or stagnant water in a mop bucket.

In some circumstances, and particularly if phorid flies are present, the drain or moth fly infestation may not be caused by the drain itself but rather by a sewage line break or crack, needing the assistance of a plumber to fix the problem. Finding and removing their water and food sources is the key to controlling drain flies.

How do you find the source of drain flies?

In some circumstances, drain flies can breed and grow in unusual places, such as beneath a loose floor tile, in the tank of a rarely used toilet, under a sink where a faulty pipe is placed, and in other places exposed to gunk.

You want to place glue boards in the infested area if you have determined that you do have drain flies but that they are not coming from the drain.

To find drain flies, follow these steps:

  • Look near plumbing appliances. Keep an eye out for tiny, black flies. Drain flies are frequently found near your toilet, shower, and sink.
  • Egg or larvae cluster. Look for any obvious egg or larvae clusters in the drain or on the drain cover’s edges. These particles could appear as tiny, translucent, or white clusters.
  • Drain fly activity. Check the room for drain fly activity in any areas with standing water or moisture. Drain flies are drawn to damp areas and can be found close to leaks or pools of water. Use a flashlight to check for drain fly activity in dark places like pipes or underneath appliances.

In order to catch drain flies, set a trap. Put a sticky trap close to the drain or plumbing fittings, or use a shallow dish filled with water and dish soap. This can assist in confirming the presence of drain flies and locating their nesting grounds.

How do I permanently get rid of drain flies?

Do the following to get rid of drain flies if you have no drain:

1. Inspect the non-drain areas

Inspect all sinks, baths, and floor areas before you go to bed. 

Each area should have a strip of transparent adhesive tape or a tiny piece of glue board placed across the middle with the sticky side. If possible, leave the glue boards or sticky tape in place over the weekend or overnight.

You may tell that an area is a drain fly breeding ground if you discover flies stuck to your glue boards.

Repeat the procedure for at least 3-5 more nights if you don’t find any drain flies to account for changes in the breeding cycle.

2. Clean the areas

The organic waste gathered in your home attracts drain flies. Your pipes may become clogged with several types of tiny organic materials over time, including food fragments, soap scum, hair, and different types of dirt deposits. This organic stuff will eventually attract drain flies.

Flush every affected area with hot water to clean them and use a hard brush on the area. To fully clear the gunk, you’ll need to pour some additional hot water.

Avoid caustic chemicals in pipes to avoid corrosion. It’s best to hire a qualified plumber to ensure that everything is done correctly.

3. Get rid of stagnant water

Drain flies are attracted to stagnant water that has turned into sludge over time. It even makes an ideal place for these critters to deposit their eggs. Make sure to use hot water and a firm brush to clean the floor. You can apply vinegar and baking soda to rinse off and discourage the drain flies from returning. You can also use bleach to kill drain flies but it has its downside such as damaging older pipes. Be sure to dry any water remnants.

4.  Clear indoor garbage and recycling areas

Keep your garbage areas clean. When garbage sits for too long, it attracts drain flies, so it’s not only a dirty drain that brings them to your home.

Introduce the habit of clearing your garbage and recycling bins regularly. Also, be sure to clean the walls and surrounding floors around your trash cans as they may contain organic materials which attract drain flies to your home.

Endeavor to clean your garbage container with hot, soapy water each time it is emptied.

5. Eliminate other outdoor sources

Apparently, the problem is not with the drain inside your home. Understand that you may have a few culprits outdoors attracting the drain flies. Sources outdoor bringing drain flies into your home include:​​​​​​

  • Garbage cans
  • Compost bins
  • Birdbaths
  • Rain barrels
  • Dog kennels

Get rid of loose organic material and stagnant water from these areas to keep drain flies at bay.

Read also: you don’t need vinegar to remove fruit flies

  1. Hi there! Question about drain flies. We just had a pipe under our slab in the kitchen repaired. (It had corroded) We had drain flies prior to the repair. The pipe was replaced. Old dirt removed. New sand replaced. Bleached applied before cementing the slab. While the repair was occurring, additional flies were coming up from the open slab into our home. We’ve been killing as many as we can. It’s been about a week since the repair and we still have the flies. We’ve been using drain gels and setting traps at night. How long will these flies persist? Is there anything else we can do? Thanks so much!

    1. Hi, Zauner. Give it up to 1 month to clear up. Those sewer/drain flies you’re still seeing after a week of repairs are likely either eggs or larvae that survived the pipe and sand replacement. You could also have another breeding site elsewhere in your home. Moreover, removing all the affected old soil is not usually possible, or at least not something the repair people will be diligent about. So, give it 3 more weeks and continue with your current treatment plan while trying to trace any other nesting zone. I’m always here to give you expert tips. Warm regards

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