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Drain Fly


Summary: The drain fly is a little pest that hang out inside drains. It looks like a tiny moth, so it is sometimes called moth fly or drain moth. These bugs love hanging out in stagnant water, so the best way to avoid them is to eliminate standing water and scrub off the slick scum from the inside of drains.

The drain fly goes by many names including filter fly, sewer fly, drain fly and drain moth. It is a teeny little bug that is commonly seen around drainpipe openings. It measures no longer that 1/5 of an inch, so it can be very hard to spot at times. It has hairy, dark wings that make it resemble a miniature moth. Fortunately, drain flies do not bite. Unfortunately, they multiply like crazy, fly out of drains and hang out on a walls and ceilings. It is not a good flier, so if you notice drain flies in a room, you will most likely find its breeding source in that room.

drainfly.jpg
credits: Steve Jacobs, PSU Entomology

You are most likely to experience an infestation of drain flies after you have been away from your home for awhile like on a vacation. These pests are often found in stagnant water. So once the drains in your home have running water flowing through them again, you can eliminate any young drain flies. Adult drain flies can escape the wrath of the drain, though. They can survive at cold and hot temperatures, so turning your water on at different temperatures will not eliminate adult drain flies from your drain.

Places that drain flies can be readily found are in moist manure, drain traps, septic tanks, garbage cans, dung, storm drains, damp leaves, inside toilet bowls that are not regularly used, in any type of drain in a garage or basement, and anywhere else that has stagnant water.

Larvae of drain flies are found in bird feeders, moss, thick mulch, or under plants or air conditioners. They feed on decaying animals and plants they find outside; indoors, they eat decaying food in drains. So if you do not clean your drain out regularly, you are practically inviting these pests in as roommates. When you see those black like worm-like larvae you know you've got a drain fly infestation.

Immature drain flies are extremely hard to identify because of their tiny size.

drainflydrain.jpg
Fly breeding location

However, you can try a simple trick to determine if drain flies are camping out in your home. Take a small plastic cup and spread a layer of petroleum jelly or vegetable oil on it. Set the cup very close to a drainpipe. Wait a couple of days and check the cup. Look closely for any larvae. They are gray with dark bands across their backs. This technique will help you not only find where the drain flies are living, but it will also help you catch them because they will get stuck in the sticky film.

Another way to find out if you have drain flies is to set some fly tape over the opening in your sink, sticky side down. Wait about 24 hours. If you see tiny flies on the tape, you know you have just been paid a visit by drain flies.

Tips to Avoid Drain Fly Infestation:

  • Keep your gutters unclogged. Drain flies love gutters full of water for them to live in.
  • Check your air conditioning unit's drain every week in the summer. Though it may seem like a hassle, it will prove to be beneficial because drain flies can reproduce quickly.
  • Make sure to keep your windows and doors closed in the summertime.
  • Buy a fine weave fiberglass window screen for your windows and patio. The small holes in a common window screen are wide enough to allow drain flies into your home. The smaller the holes, the less chances you have of tiny pests flying in.

Tips to Eliminate Drain Flies:

  • The most important task in getting rid of a drain fly infestation is to eliminate their breeding site. If you can remove the stagnant water the larvae grow in, they will have nowhere to reproduce.
  • Spray your drains or rooms where adult drain flies are found with an aerosol insecticide spray labeled for flies. Sprays used on houseflies will work on drain flies.
  • Get rid of any decaying food you have in your home that the flies can feed on. Clean out any areas that drain flies are attracted to, and definitely clean out your drains thoroughly.
  • If found in your bathroom or another room with tile, grout your tiles. This will help remove any moisture that has accumulated.
  • Check for wet lint underneath your washing machine and get rid of it.
  • Get rid of the gunk building up in your drain. Drain fly larvae love to eat this stuff. Do not pour bleach down the drain. Bleach kills bateria. It is not an insecticide. There are products like DF 5000 Drain Cleaner, but it is just as easy to use a toilet brush to scrub out the drain. Really tough cleaning jobs may require some Drano to really clean it out.
If you have drain flies breeding under the floor slab you may have to open the slab and have all the contaminated soil removed. These flies live in the algae and mold that grows in wet environments. Do not try to spray more liquid pesticides into cracks in the slab. It will only make matters worse. The moisture problem must be located and fixed. Call a plumber, not an exterminator.




Comments

Caroline
13 Oct 2009, 22:32
I have these wonderful drain flies in my upstairs master shower stall (fiberglass one piece). They appear to possibly be coming from the seal around the inside of the shower wall/shower door. It does have mildew in it, but the rest of the shower is clean. I spray it with bleach often, but it still continues to have mildew and larvae. Can that be torn off and replaced to get rid of the problem?
Any advice you could give I would really appreciate! Thanks, Caroline
Amber
01 Dec 2009, 15:27
Wouldn't it be prudent to mention that some of the people who have posted questions here may actually have fungus gnats? I started some vegetables from seed under UV lights in a spare room. The potting soil I used had fungus gnats in it and they started hatching out this summer. I have removed all plants, soil and plant debri from the house 10 weeks ago and vaccumed thoroughly and I still have fungus gnats hatching out and flying around the house. Lately I have been finding them in the bathrooms and kitchen. I had one fly out of the garbage disposal the other day as I turned the water on. Even though fungus gnats prefer to lay their eggs in soil they can set up house wherever moist areas where mold and fungus may be present. They can set up house in wall voids and behind loose tile if mold and fungus are present for a food source. I suspect they may even try to lay eggs in drains. The adults only live 5-7 days but during that time they can lay up to 300 eggs, typical in batches of 10-30. They can make their way into wall voids, particularly if there is wet decaying wood. The best way to check if they are in the walls is to remove the electrical plate and place strips of sticky tape over it with gaps in it - some will get caught in the tape if they are present.
Amber
01 Dec 2009, 16:08
I think it would be prudent to mention that people who have posted questions here may actually have fungus gnats rather than drain flies. Particularly if they haven't been seeing them flying out of their drains. I currently have a fungus gnat infestation and it all started when I planted some vegetable seed starts and the potting soil I used was infested with fungus gnat eggs. The gnats began hatching out of the soil soon after I began watering my seedlings which were sitting under UV grow lights on racks set up in a spare room. After trying to kill them by using BT Israelis soil drenches I finally ended up removing every plant start and house plant in my entire house. I then did a thorough vaccuming to remove any remaining spilled potting soil and plant debri. I sealed off the room that was the original source of my outbreak and now 10 weeks later I still find a few fungus gnats flying around the house every day. Since adult fungus gnats only live 5-7 days it seems that the adults have found new fungus and mold sources to lay their eggs, and hence, the cycle continues. Lately I am finding more and more of them in my kitchen and bathrooms where moisture is always present. I suspect that some may have set up house behind some loose old tile in a bathroom that needs remodeling and wonder if others are trying to lay their eggs in moist sink drains, especially after having one fly out of my garbage disposal as I was turning on the water on just the other day. Fungus gnats prefer to lay their eggs in moist fungused or debri infested soil but they have been known to set up house in moist areas where mold or fungus is present. They also can find their way into wall voids through electrical outlets and lay eggs in moist decaying wood. So if you have had a water leak and have dry rot you may have an infestation somewhere in your wall voids.
Debbie
12 Dec 2009, 17:53
How do you tell if the bugs are fungus gnats or drain flies. We have a horrible infestation in our kitchen but I have no live plants in my house. I have septic--does that matter. I have dumped so much stuff down the drain in hopes of ridding them but they keep multiplying and flying inset sprays do not even kill the adult ones. They are attracted to weird things like the paper towel roll but not pest tape. Help--Christmas is coming and we cannot cook in our kitchen as they are everywhere.
Judy
11 Jan 2010, 02:15
Fungus gnats look like, well, gnats or fruit flies (as an aside, I have gotten rid of fungus gnats in houseplants with a combination of sticky traps, Gnatrol and watering more cautiously). They seem madly attracted to yellow sticky traps, and I rarely saw them at any great distance from a plant.

The drain flies I have, on the other hand, resemble tiny dark moths more than they do fruit flies. We're seeing them mostly around a bathroom where we typically don't use the tub. We haven't made a concerted effort to get rid of them yet, but now there's more incentive to get the leak in the tub fixed so we can start running water there again. Never saw 'em before we stopped using that tub.
Michele
23 Feb 2010, 20:27
** Make sure you are looking EVERYWHERE ** For months I've been trying to figure out where these guys are coming from... They are found on every wall of my apartment. First I thought my snake tank (moist soil & water dish, then I thought somewhere around the filter of my fish tank, I only have four drains and I use and clean them all regularly. I have even been looking around the water drainage trays under all my flower pots. I just decided to put my giant dying fern outside and came back in to find LITTLE MOVING SPECKS on the table under where the fern was! Right by the chair I sit in all the time! Ick I feel itchy all over! It makes sense but that was just not a place I thought to look. I hope this is the end of it and I will probably save a fortune on toilet paper, since everyday I'm smushing and flushing 10-20 of them with TP squares. I hope this helps someone.
Suzanne Benson
04 Mar 2010, 18:59
We have fungus gnats or drain flies and they are all over the house, especially in the bathrooms. We have tried several products from our exterminator and had the outside sprayed by another exterminator. The spraying worked for a few weeks, and no luck with the products in the drains. We have had this problem since November. We are on septic system. Will it help to have it pumped? What else can we use?
margaret
07 Mar 2010, 11:55
hi weve recently noticed tiny black flies in the toilet area im killing about 5 a week please help this is really getting me down am that fed up im on the verge of moving house and its getting to a stage where im looking around before actually going to toilet we also have a dog which can open the door and am worried he licks the fly spray weve been spraying
Suh
29 Mar 2010, 19:31
I have been using a method that works for me. It has to be done on a weekly basis and it doesn't involve any chemicals nor scrubbing. The drain flies are found only in my ensuite bathroom so that explains which drain they come from. I use a thin cloth to cover the drain hole and pour boiling hot water into it through the cloth, trapping the flies in the drain pipe and scalding the larvae. I probably pour in about 3/4 litres of very hot water (from my shower tap) into the drain pipe. Hope this helps.
Shawn
13 Apr 2010, 13:22
I moved into a house that had these pests in the bathroom, it took several weeks to get rid of them but here's how I did it:
I used about a half a cup of Drano and let it set overnight in the trap, I set out a bowl of apple juice(apple cider will also work) with a few drops of liquid soap. I then closed the batroom door overnight. In the morning I noticed the bowl caught a lot of the adults. I filled the sink with hot water and opened the drain, I did this several times. I had to do this for evrynight for about a week to get all of the adults and eggs.
Shawn
13 Apr 2010, 17:34
Don't forget about the toilet:
Shut off the water and drain the tank, use a bleach/water solution to clean the tank and throw the papertowels in the trash outside.
bill
16 May 2010, 08:41
i am having a drain fly problem in my kitchen and garage. my slab is sagging in the kitchen.i had a plumber scope the pipes and he said he found nothing. i was an exterminator for 16 yrs and my knowledge of these was always a crack sewer line. do you agree ?
Ask the Exterminator
16 May 2010, 16:08
Could be a cracked sewer line or other leaking pipe. Have you checked the tile on the kitchen floor to be sure the flies are not under the tile?
Viv
04 Jun 2010, 00:32
NIGHTMARE, IS THE WORD==finally down to zero drain flies, i hope---used drain gel by clorox, drain foam by clorox, hot water, cleaned, cleaned, sprayed bug spray (body kind) lol and today we did not see any, also used Rid drain box kind and put that in commodes. I cannot tell u how many of these flies were dead when we got home from vacation, they were only in one bathroom in home--i threw everything out and did find where some shampoo had tilted over in a drawer--cleaned that out washed all towels and rug--took it all out and cross ur fingers -i hope they are gone---thanks for help
Angie
22 Jul 2010, 05:44
Please help - these pesty creatures have laid eggs in my toilet. Black larvae like worms keep coming up in batches when I pour bleach into the toilet. About 30-50 each time. I wait an hour or two for them to accumulate, try to manually smash them, and then flush several times. But they keep on coming. Where in the toilet do they live? What can I put in their besides bleach to get rid of them?
Ask the Exterminator
22 Jul 2010, 10:30
Bleach is not a pesticide. Stop using bleach. Check under the rim of the toilet. They are not coming from under the water line, but more likely where from where the water flows into the toilet. Just use regular toilet bowl cleanser.
angie b
29 Jul 2010, 13:54
Hi, my mum has an infestation of tiny flies, they fly but when on the window or walls, they seem to jump about, they aren't pet fleas. Some guys from the waste unit are dealing with it but haven't a clue what they are doing. The flies get everywhere and mum thinks she's been bitten, they look similar to midges in size, the drain aren't very good where she lives in sheltered accomadtion and her toilet has been filling up a bit too much with water, do you think these could be drain flies? One theory the came with was that they were coming from some conifers across the way, but I don't think they are. These flies can also be found on the edging of the carpet as well, could they be coming from under the floor? I seem to think it was an ashfelt floor. please can you advise me as my mum is very distressed
thanks
ANGIE
Ask the Exterminator
30 Jul 2010, 09:29
Could be springtails, but I cannot ID without a photo.
Lela G
06 Aug 2010, 09:42
We had a leaky pipe under our kitchen sink and that's how we first got drain flies but that was months ago! I've done everything from pour Draino down the drains and then hang fly strips to setting off bombs in the house. So now I'm going to start thinking "au naturale". I was told to use a concoction of vinegar, baking soda and salt down the drains overnight, then plugging the drains so that nothing can escape. I will tell you how well it works.
Ask the Exterminator
06 Aug 2010, 11:16
I'm betting the flies are not coming from the drain. The easiest way to tell is put wide Scotch tape to cover the drain overnight. If flies are inside the drain they will stick to the tape as they try to leave the drain.

I'm guessing the fly breeding is under the floor covering. Use the trap trap method over some of the tiny grout lines in the floor to see if you capture any flies. If you do, you will have to lift the floor covering to dry out any moisture that has accumulated in order to halt the fly breeding.
Terri Y
10 Aug 2010, 02:41
I purchased a product over the internet (it smelled like orange) and have poured it down all drains in my home. The basement of our home is over-run with these drain flies and I now believe that they are in the drainage for our central air. My husband just had surgery and is unable to do anything. I don't know whether to call a plumber, central air tech or exterminator?! Thanks!!!
Ask the Exterminator
10 Aug 2010, 09:16
Did you read the label? Does the label list drain flies as one of the target pests? Did you follow the application instructions? Have you determined that the flies are, in fact, coming from the drains? One way to determine if the flies are coming from the drain is to totally cover the drain opening with wide Scotch tape. If the flies are in the drain they will stick to the tape as they try to emerge from the drain.
Amber
31 Aug 2010, 20:59
Please help!!! We are over run by these horrible creatures! I had an exterminator come for carpenter ants. When he came we had a few drain flies in the basement but after he sprayed it got worse. And it keeps getting worse. We had someone come and fix one drain opening that had no seal on it and I have been keeping water in the traps to seal the flies out. I was told that we have bell traps and you have to keep water in them to seal them. We also had our septic pumped. What else can be done? The exterminator has been to our home 3 times in the lase month and a half. Please Please Please help!!!
Ask the Exterminator
01 Sep 2010, 14:21
You need to confirm that the flies are, indeed, coming from the drains. A simple way to do this is to cover the drain opening with wide Scotch tape. The next morning you can check the tape. If there are no flies, the drain is not the source. Do the same thing over tiny cracks in the floor grout, too. These flies can breed under floor tiles.
Amy
01 Sep 2010, 20:50
I have drainflies in my house. They are all over the basement. However, the room I see them in has no windows, no drains, and no stagnant water..ect. There is a room with a windowsill...Where can they be coming from? The seem to cling to the basement concrete wall. Are they coming through the cracks in the wall?? I'm confused.
Patricia
02 Sep 2010, 00:51
I have a finished basement with a bathroom and also a room with a sewage ejector pump. We have have a septic tank as well. I happened to notice about five of these drainflies when I installed night lights. I have never noticed anything before the lights were placed. Does this mean I have a infestation? I do not know where to begin looking since there are so many pumps and drains in the basement. I am hoping these are not drainflies but everything I have read suggests they are. Thanks for your help.
Ask the Exterminator
02 Sep 2010, 08:40
Amy & Patricia:

Please try the Scotch tape trick I talked about in the comment previous to yours. You need to determine where they are emerging.
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