How do you get rid of sewer flies?

Key facts

• University of Arkansas extension, cleaning period for an infested drain: "Control of an infested drain requires thorough cleaning and maintenance for at least 3 weeks or longer to break the life cycle."

  Source: University of Arkansas Cooperative Extension, Drain Flies - What are they? How do I get rid of them?, read 24 October 2026.

• University of Kentucky entomology, drain fly life cycle at room temperature: "The drain fly life cycle takes from about 10 to 15 days at about 70° F."

  Source: University of Kentucky Entomology, Drain Flies or Moth Flies (ENTFACT-615), read 24 October 2026.

• Alabama Cooperative Extension, drain fly life cycle range: "The life cycle ranges from 8 to 24 days, depending on temperatures and humidity."

  Source: Alabama Cooperative Extension System, Drain Flies in the Home: Identification and Management (ANR-3235), read 24 October 2026.

• Alabama Cooperative Extension, eggs per female and hatch time: "Eggs typically hatch within 2 days." "A female fly lays between 30 and 100 eggs, often in irregular masses."

  Source: Alabama Cooperative Extension System, Drain Flies in the Home: Identification and Management (ANR-3235), read 24 October 2026.

• University of Arkansas extension, larval and pupal stages: "feeding on decaying organic matter for approximately 18 days before pupating, which takes about 5 days."

  Source: University of Arkansas Cooperative Extension, Drain Flies - What are they? How do I get rid of them?, read 24 October 2026.

• University of Arkansas extension, adult size: "Adults can vary in color from dark to light gray or tan, with spots on their wings, and a total body length of 2-4 mm"

  Source: University of Arkansas Cooperative Extension, Drain Flies - What are they? How do I get rid of them?, read 24 October 2026.

• Alabama Cooperative Extension, insect growth regulator reapplication interval: "IGRs are lowtoxicity products and require thorough coating of the pipe sides and reapplication (generally every 2 to 4 weeks) for continued effectiveness."

  Source: Alabama Cooperative Extension System, Drain Flies in the Home: Identification and Management (ANR-3235), read 24 October 2026.

Why am I getting sewer flies?

They breed where water stands. University of Kentucky entomologists say drain flies develop in standing water, so most commonly they are seen after returning home from a vacation or period of extended travel, and that finding many flies over several weeks usually means a relatively permanent breeding site that must be found and eliminated. University of Arkansas extension says they mostly inhabit drains that are used infrequently, such as a guest bathroom shower drain, and that larvae can also be introduced from sewer pipes that burp or back up into a home.

Source: University of Arkansas Cooperative Extension, Drain Flies - What are they? How do I get rid of them?, read 24 October 2026.
Source: University of Kentucky Entomology, Drain Flies or Moth Flies (ENTFACT-615), read 24 October 2026.

University of Arkansas extension, read 24 October 2026, gives the names: "Other names for this insect include drain flies, sewer flies, filter flies or bathroom flies." "Due to their hairy appearance, with dense setae on their bodies and long antennae, these insects are also referred to as moth flies or moth midges." It adds: "Adults can vary in color from dark to light gray or tan, with spots on their wings, and a total body length of 2-4 mm"

Source: University of Arkansas Cooperative Extension, Drain Flies - What are they? How do I get rid of them?, read 24 October 2026.

The University of Kentucky's entomology fact sheet on drain flies, read 24 October 2026, lists common indoor sites: "They can live most anywhere that water accumulates for a week or more." "Common indoor sites include the fine slime layer that develops along the water surface in infrequently used toilet bowls and tanks, in sink or floor drains in basements or garages, or drain pans under refrigerators."

Source: University of Kentucky Entomology, Drain Flies or Moth Flies (ENTFACT-615), read 24 October 2026.

Alabama Cooperative Extension's guide, read 24 October 2026, lists among breeding sites: "Leaking pipes behind a wall or under a concrete slab. The resulting wet organic debris can harbor larvae."

Source: Alabama Cooperative Extension System, Drain Flies in the Home: Identification and Management (ANR-3235), read 24 October 2026.

Does pouring bleach or vinegar down the drain kill drain flies?

Not in a way that ends the problem. Alabama Cooperative Extension says larvae live in the protective slime on the side of the drainpipe, so pouring baking soda, bleach, vinegar, or boiling water down the drain is ineffective and may damage the drainpipe. University of Kentucky entomologists say pouring hot water down the drain may provide short-term control, and that larvae are able to trap air bubbles and remain submerged for a day or more. Utah State extension says larvae hide behind scum, making attempted treatments with boiling water, pesticides or other chemicals ineffective. Alabama extension says the most effective method is to scrub the drain opening with a stiff brush and drain cleaner to remove all the slime and sludge.

Source: Alabama Cooperative Extension System, Drain Flies in the Home: Identification and Management (ANR-3235), read 24 October 2026.
Source: University of Kentucky Entomology, Drain Flies or Moth Flies (ENTFACT-615), read 24 October 2026.
Source: Utah State University Extension, Drain (Moth) Fly, read 24 October 2026.

If you have already poured cleaners down a drain, mind the mix. The Alabama guide, read 24 October 2026, warns: "In addition, ammonia and bleach should never be used together (their chemical reaction releases hazardous gas)"

Source: Alabama Cooperative Extension System, Drain Flies in the Home: Identification and Management (ANR-3235), read 24 October 2026.

How do you find which drain the flies come from?

Trap the adults as they come up. University of Arkansas extension says a clear plastic cup or glass jar, coated inside with vegetable oil or petroleum jelly, can be placed over a suspected drain to trap adults emerging from it. University of Kentucky entomologists say such cups can be inverted over drains for several days, and if these are not productive, then expand the search. Penn State Extension says to place a jar over the outlet or tape a plastic bag over the opening of the overflow outlet. The Arkansas sheet says a population may be emerging from more than one drain or breeding site simultaneously, and to inspect and clean all potential drains in the vicinity.

Source: University of Arkansas Cooperative Extension, Drain Flies - What are they? How do I get rid of them?, read 24 October 2026.
Source: University of Kentucky Entomology, Drain Flies or Moth Flies (ENTFACT-615), read 24 October 2026.
Source: Penn State Extension, Moth Flies in the Home, read 24 October 2026.

The Alabama guide, read 24 October 2026, gives a tape version of the test and the signs of possible breeding sites: "Place clear tape over the drain opening (sticky side down), leaving a small section exposed for airflow." "Slow drainage, bubbling, and foul odors from drains are signs of possible breeding sites."

Source: Alabama Cooperative Extension System, Drain Flies in the Home: Identification and Management (ANR-3235), read 24 October 2026.

If no indoor trap catches anything, the Kentucky fact sheet says to expand the search, and it points outdoors: "These should be addressed if adults do not appear to be emerging from within the house." "Low, wet areas where air conditioning units drain, or clogged guttering are excellent places for these insects to develop."

Source: University of Kentucky Entomology, Drain Flies or Moth Flies (ENTFACT-615), read 24 October 2026.

How long does it take to get rid of drain flies?

Plan on weeks of steady cleaning, not one treatment. The University of Kentucky says the drain fly life cycle takes from about 10 to 15 days at about 70° F; Alabama Cooperative Extension says it ranges from 8 to 24 days, depending on temperatures and humidity; and University of Arkansas extension says control of an infested drain requires thorough cleaning and maintenance for at least 3 weeks or longer to break the life cycle.

Source: University of Kentucky Entomology, Drain Flies or Moth Flies (ENTFACT-615), read 24 October 2026.
Source: Alabama Cooperative Extension System, Drain Flies in the Home: Identification and Management (ANR-3235), read 24 October 2026.
Source: University of Arkansas Cooperative Extension, Drain Flies - What are they? How do I get rid of them?, read 24 October 2026.

The Alabama guide, read 24 October 2026, gives the egg numbers: "Eggs typically hatch within 2 days." "A female fly lays between 30 and 100 eggs, often in irregular masses."

Source: Alabama Cooperative Extension System, Drain Flies in the Home: Identification and Management (ANR-3235), read 24 October 2026.

The Arkansas sheet gives the stages: "feeding on decaying organic matter for approximately 18 days before pupating, which takes about 5 days." "Their total life span is about 35 days."

Source: University of Arkansas Cooperative Extension, Drain Flies - What are they? How do I get rid of them?, read 24 October 2026.

Should you pour insecticide down the drain for drain flies?

No. University of Arkansas extension says no insecticide products are registered for use in drains or sewer systems, and that these products are unlikely to work against the intended pests and can cause significant damage to a sewer or septic system. University of Kentucky entomologists say do not pour insecticides down drains to kill drain flies. Washington State University's fact sheet lists none recommended under chemical management, and Alabama Cooperative Extension says chemical control inside homes is generally unnecessary and discouraged. Going after the adults does not end it either: the Arkansas sheet says killing adult flies is not effective control, and that sticky fly paper or UV-light traps can capture some adult flies, but will not eliminate an infestation.

Source: University of Arkansas Cooperative Extension, Drain Flies - What are they? How do I get rid of them?, read 24 October 2026.
Source: University of Kentucky Entomology, Drain Flies or Moth Flies (ENTFACT-615), read 24 October 2026.
Source: Washington State University Pestsense, Moth flies (drain flies), read 24 October 2026.
Source: Alabama Cooperative Extension System, Drain Flies in the Home: Identification and Management (ANR-3235), read 24 October 2026.

The Alabama guide, read 24 October 2026, describes one chemical step for indoor breeding sites: "If physical removal of indoor larval breeding sites is impractical, insect growth regulators (IGR), such as hydroprene or methoprene, may be applied directly to larval habitats to disrupt development." "IGRs are lowtoxicity products and require thorough coating of the pipe sides and reapplication (generally every 2 to 4 weeks) for continued effectiveness." It also says: "Chemical control should be considered only as a last resort."

Source: Alabama Cooperative Extension System, Drain Flies in the Home: Identification and Management (ANR-3235), read 24 October 2026.

Any product you do use is bound by its label. EPA's introduction to pesticide labels, read 24 October 2026, says that "pesticide labels are legally enforceable" and: "In other words, the label is the law."

Source: US EPA, Introduction to Pesticide Labels, read 24 October 2026.

Are sewer flies harmful to your health?

Alabama Cooperative Extension says drain flies are generally considered more of a nuisance than a health threat. University of Arkansas extension says they are not attracted to human foods and do not bite or sting humans or other animals, but that their presence suggests a rich source of moist organic material in stagnant water in the vicinity. The Alabama guide adds that in some cases drain flies may trigger allergic reactions in sensitive individuals. Washington State University says that occasionally, when adult numbers become excessive, they have been implicated in cases of inhalant allergy.

Source: University of Arkansas Cooperative Extension, Drain Flies - What are they? How do I get rid of them?, read 24 October 2026.
Source: Alabama Cooperative Extension System, Drain Flies in the Home: Identification and Management (ANR-3235), read 24 October 2026.
Source: Washington State University Pestsense, Moth flies (drain flies), read 24 October 2026.

Can you clear sewer flies yourself, or call a plumber?

Cleaning the drains, traps and overflows you can reach with a brush is the part you can do yourself, and the extension sheets give those steps. Hand it over when the source sits where you cannot reach or clean it, such as a wall void, a slab, a crawlspace or an outside sewage line, or when a drain is clogged rather than slimy. This is practical reasoning, not legal advice and not a finding from any agency.

Source: Alabama Cooperative Extension System, Drain Flies in the Home: Identification and Management (ANR-3235), read 24 October 2026.
Source: University of Arkansas Cooperative Extension, Drain Flies - What are they? How do I get rid of them?, read 24 October 2026.
Source: Utah State University Extension, Drain (Moth) Fly, read 24 October 2026.

1. Find the source drain first with an oiled cup or jar over each drain; the Kentucky sheet says such cups can be inverted over drains for several days. The Arkansas sheet says of an oiled cup or jar: "This will effectively trap adults emerging from the drain."

   Source: University of Arkansas Cooperative Extension, Drain Flies - What are they? How do I get rid of them?, read 24 October 2026.
   Source: University of Kentucky Entomology, Drain Flies or Moth Flies (ENTFACT-615), read 24 October 2026.

2. Take apart what you can reach. Alabama extension: "It is best to remove the sink pivot, stopper, shower cover, and drain trap and clean them with a biodegradable cleaner or clean water before putting them back on."

   Source: Alabama Cooperative Extension System, Drain Flies in the Home: Identification and Management (ANR-3235), read 24 October 2026.

3. Scrub the inside of the drain and trap. Utah State extension: "Remove larval habitat by using a hard bristle brush to remove the scum film from inside the drain." Penn State gives the tools: "This requires cleaning sinks, drain pipes, and traps with a stiff wire brush or by steam."

   Source: Utah State University Extension, Drain (Moth) Fly, read 24 October 2026.
   Source: Penn State Extension, Moth Flies in the Home, read 24 October 2026.

4. Follow the brush with a biological or enzyme cleaner for the pipe you cannot reach. Washington State University: "Biological drain cleaners (non-toxic) can be used to remove the organic slime layer and organic debris in the drain." Alabama extension: "An enzymatic drain cleaner or foaming drain treatment can be used to reach deep into drainpipes."

   Source: Washington State University Pestsense, Moth flies (drain flies), read 24 October 2026.
   Source: Alabama Cooperative Extension System, Drain Flies in the Home: Identification and Management (ANR-3235), read 24 October 2026.

5. Clean every drain nearby, not only the one that caught flies, as the Arkansas sheet advises: "Inspect and clean all potential drains in the vicinity to increase success of control measures."

   Source: University of Arkansas Cooperative Extension, Drain Flies - What are they? How do I get rid of them?, read 24 October 2026.

6. Run water through rarely used sinks, tubs and toilets. The Kentucky sheet says: "Usually, they disappear soon after normal household activity resumes and water starts to move again through toilets and drain traps."

   Source: University of Kentucky Entomology, Drain Flies or Moth Flies (ENTFACT-615), read 24 October 2026.

7. Repeat the cleaning on a schedule for at least the period the Arkansas sheet gives: "Control of an infested drain requires thorough cleaning and maintenance for at least 3 weeks or longer to break the life cycle."

   Source: University of Arkansas Cooperative Extension, Drain Flies - What are they? How do I get rid of them?, read 24 October 2026.

8. Deal with the adults last. Alabama extension: "Once breeding sources have been removed, adult flies can be easily killed by swatting them or vacuuming them up."

   Source: Alabama Cooperative Extension System, Drain Flies in the Home: Identification and Management (ANR-3235), read 24 October 2026.

Hire a pro when the flies point to a pipe problem rather than a dirty drain:

• Flies keep coming back after every drain is clean. Arkansas: "An ongoing or recurring infestation, despite careful sanitation of all drains, can indicate a broken pipe or leak under a slab or in a crawlspace beneath the home."

  Source: University of Arkansas Cooperative Extension, Drain Flies - What are they? How do I get rid of them?, read 24 October 2026.

• The source is out of reach or outside the house. Alabama: "If the fly breeding sites are inaccessible (e.g., within a wall void) or the breeding source is at an off-site septic tank and sewage system, it is best to call a professional plumbing service."

  Source: Alabama Cooperative Extension System, Drain Flies in the Home: Identification and Management (ANR-3235), read 24 October 2026.

• The drain is clogged, not just slimy. Alabama: "In the case of a clogged drain, use a drain snake (drain auger or toilet jack) or call a plumbing router service."

  Source: Alabama Cooperative Extension System, Drain Flies in the Home: Identification and Management (ANR-3235), read 24 October 2026.

• Flies are coming from voids, crawl spaces or slabs. Utah State: "If flies are coming from voids, crawl spaces or slabs, fix the moisture issue causing the problem and seal."

  Source: Utah State University Extension, Drain (Moth) Fly, read 24 October 2026.

• Finding the leak means opening a wall, shower pan or slab. Alabama: "Sometimes you may also need to drill a hole into the wall behind the shower, the area under the shower pan or bathtub, or the slab where the drainpipe leaks."

  Source: Alabama Cooperative Extension System, Drain Flies in the Home: Identification and Management (ANR-3235), read 24 October 2026.

• The yard or sewer line is the source. Alabama lists among outdoor sites "areas soaked with backup from a broken in-ground sewage pipe" and San Diego's sewer lateral guide says: "If the lateral is broken, you will have to repair the lateral."

  Source: Alabama Cooperative Extension System, Drain Flies in the Home: Identification and Management (ANR-3235), read 24 October 2026.
  Source: City of San Diego, Sewer Laterals guide (PDF), read 24 October 2026.

What to ask for in writing if you hire:

• Where the breeding source was found: which drain, trap, overflow, wall, slab or line.
• Whether the cleaning covers the whole drain run, the way Arkansas describes high-pressure service: "High-pressure drain cleaning services can eliminate organic food near the end of the drain, as well and through the entire length of the drain, reducing the likelihood of larvae returning."

  Source: University of Arkansas Cooperative Extension, Drain Flies - What are they? How do I get rid of them?, read 24 October 2026.

• If a broken pipe is found, exactly where it sits relative to your property line. San Diego's guide: "The entire length of the sewer lateral, extending from your home or building to its point of connection with the City sewer main underneath the street, is your private property."

  Source: City of San Diego, Sewer Laterals guide (PDF), read 24 October 2026.

• The name of any product put into the drain, so you can read its label yourself.

  Source: US EPA, Introduction to Pesticide Labels, read 24 October 2026.

• What cleaning you should keep doing afterwards, and for how many weeks, since the Arkansas sheet says control of an infested drain requires thorough cleaning and maintenance for at least 3 weeks or longer.

  Source: University of Arkansas Cooperative Extension, Drain Flies - What are they? How do I get rid of them?, read 24 October 2026.

What should you check before calling the flies gone?

Check the whole chain from source to schedule: the Arkansas sheet says a population may be emerging from more than one drain or breeding site simultaneously. Work through this list and keep your trap results with the dates.

Source: University of Arkansas Cooperative Extension, Drain Flies - What are they? How do I get rid of them?, read 24 October 2026.

1. Every drain and overflow in the affected rooms has had a cup, jar or tape test.

   Source: University of Arkansas Cooperative Extension, Drain Flies - What are they? How do I get rid of them?, read 24 October 2026.
   Source: Penn State Extension, Moth Flies in the Home, read 24 October 2026.

2. The drain that caught flies has been taken apart, brushed and put back together.

   Source: Alabama Cooperative Extension System, Drain Flies in the Home: Identification and Management (ANR-3235), read 24 October 2026.
   Source: Utah State University Extension, Drain (Moth) Fly, read 24 October 2026.

3. A biological or enzyme cleaner has gone into the pipe beyond the brush.

   Source: Washington State University Pestsense, Moth flies (drain flies), read 24 October 2026.
   Source: Alabama Cooperative Extension System, Drain Flies in the Home: Identification and Management (ANR-3235), read 24 October 2026.

4. Rarely used sinks, tubs and toilets have had water run through them.

   Source: University of Kentucky Entomology, Drain Flies or Moth Flies (ENTFACT-615), read 24 October 2026.

5. Outdoor spots the Kentucky sheet names, low, wet areas where air conditioning units drain and clogged gutters, have been checked.

   Source: University of Kentucky Entomology, Drain Flies or Moth Flies (ENTFACT-615), read 24 October 2026.

6. Cleaning has continued for at least the period the Arkansas sheet gives: "Control of an infested drain requires thorough cleaning and maintenance for at least 3 weeks or longer to break the life cycle."

   Source: University of Arkansas Cooperative Extension, Drain Flies - What are they? How do I get rid of them?, read 24 October 2026.

7. No insecticide has gone down any drain, in line with the Kentucky sheet: "Do not pour insecticides down drains to kill drain flies."

   Source: University of Kentucky Entomology, Drain Flies or Moth Flies (ENTFACT-615), read 24 October 2026.

8. If flies still appear after all of this, a plumber has been asked to look for a broken pipe or leak.

   Source: University of Arkansas Cooperative Extension, Drain Flies - What are they? How do I get rid of them?, read 24 October 2026.

Who sees your contact details when you post on InstaBids?

Contact details stay hidden until the homeowner picks a contractor and they confirm the connection.

Source: InstaBids process and privacy, live-page excerpts, read 24 October 2026.

Sources for the facts on this page

• University of Arkansas Cooperative Extension, Drain Flies - What are they? How do I get rid of them?, read 24 October 2026
• University of Kentucky Entomology, Drain Flies or Moth Flies (ENTFACT-615), read 24 October 2026
• Alabama Cooperative Extension System, Drain Flies in the Home: Identification and Management (ANR-3235), read 24 October 2026
• Penn State Extension, Moth Flies in the Home, read 24 October 2026
• Washington State University Pestsense, Moth flies (drain flies), read 24 October 2026
• Utah State University Extension, Drain (Moth) Fly, read 24 October 2026
• US EPA, Introduction to Pesticide Labels, read 24 October 2026
• City of San Diego, Sewer Laterals guide (PDF), read 24 October 2026
• InstaBids process and privacy, live-page excerpts reviewed 24 October 2026.