Drain Flies

What do drain flies, moth flies or sewer fiies look like?  

  • Often referred to as: moth flies, drain flies or sewer flies—they are yellowish, brownish-gray, or blackish in color. 
  • Drain flies are 1/16 to 1/4 inch long; larvae – 1/8 to 3/8 inch long.
  • Moth flies are very delicate flies with pointed, leaf-shaped, white-speckled wings held roof-like over their backs when at rest.
  • They are “hairy” and if touched, leave behind a greyish dry, powdery residue.

What are the habits of drain flies, moth flies or sewer flies? 

  • The females deposit 30 – 100 eggs in the “jelly-like” film that line the water-free portions of inner drain pipes.
  • Developmental time (egg to adult) is 7- 28 days.
  • The life-span of adult flies is no more than two weeks. 
  • Moth fly larvae feed on algae, fungi, bacteria, and sludge.
  • Adult flies are poor fliers and are found in great numbers resting on walls or flying delicately in the area where they developed (often in/around bathrooms). 

What kind of damage results from Drain, Moth, or Sewer Flies:

  • Moth flies or drain flies become a nuisance and an annoyance within some homes or structures (when they breed in the liquids found in drains, dirty garbage containers, sludge and septic tanks).

What should I look for when I have found drain, moth or sewer flies? 

  • Drain flies may emerge as a function of poorly maintained drains in commercial establishments such as: bathroom floor drains, mechanical spaces, food service facilities, plugged or unused garbage disposals.  
  • Sometimes, sewer lines break beneath the slab and the subsequent leaking sludge creates a condition conducive and suitable for breeding.  
  • Specifically, black slime in drains, broken drain pipes, e.g., no water in plumbing traps, very moist accumulations of decaying organic matter, e.g., plugged or unused garbage disposal, dirty evaporation pan, e.g., dehumidifier, air conditioner, refrigerator, etc., are all suitable shortcomings that can create problems with these nuisance flies. 

How do I control and kill drain, moth, and sewer flies?

  • Infestations that develop in drains can be eliminated by scrubbing the inner drain sleeves with a brush and sink-cleaning materials followed by very hot water (for rinsing)
  • It is important to scrub the drain from the surface to the depth of the trap in order to remove the organic matter lining each pipe/drain.  
  • Simply pouring hot water, bleach or other household products will not eliminate the organic matter or the fly infestation. 
  • If the drain trap is not holding water, it should be inspected and repaired. To prevent water evaporation in the trap of seldom-used drains, a small amount of mineral oil should be placed on the surface of the tap water (to slow the evaporation process).
  • Large numbers of adult flies are easily controlled using a vacuum.  However, if the “source” of the fly infestation is unknown, vacuuming “only” will not resolve these problems.  
  • “Smoke testing” is often employed by Innotech Pest Management personnel in an effort to identify breaks within sewer lines, waste lines or riser lines—that may be contributing to the overall infestation.
  • Aerosolized insecticides such as PI may be used initially to knock-down adult flies temporarily.  
  • Enzymatic agents such as Biozyme may be used in combination with scrubbing and organic matter removal efforts in order to accelerate the breakdown of decomposing organic matter. 

At Innotech Pest Management, we know that dealing with moth flies, sewer flies and drain flies is a messy job.  If you need assistance identifying, analyzing and treating these infestations, contact our team to schedule an evaluation and estimate to resolve your problems.