Drain fly infestation - DIY Chatroom

marksto · 09-11-2008, 04:41 PM

I've been fighting a persistent, severe infestation of drain flies in my home for many months. I'm at my wits end and looking for help in figuring out exactly where they are hatching so I can eliminate them. Here's what I know:

I am averaging 50-100 flies a day that spread throughout my small home but definitely originate in my one small bathroom. I know this because if I close the bathroom door they all collect there and not elsewhere in the home. They migrate towards lights, windows, and bright surfaces.
I keep both drains (sink and tub) sealed off at all times when not in use but I get them anyway, so they are not coming from the drains. I have also repeatedly cleaned the toilet tank and bowl including under the rim.
The septic tank is just outside of the bathroom, and I have sealed off all possible channels I know of for ways they might get in the home from the septic apart from the drains. I have sealed the open space beneath the drain plug lever, the drain spout, and checked for any wall cracks that might lead to the space behind the wall which in turn might allow access from the septic area.
I keep the room clean, and are no known loose tiles or other areas where mold or slime might form and allow them to breed..

If the drain flies are breeding in the bathroom, would I be seeing larvae somewhere? If so, how big are they? Any other signs, symptoms, or techniques involved with identifying breeding areas?

These things are unbelievable. At times I can shut the bathroom door, kill all that are there with flying insect killer, and stand there motionless and within a few minutes more appear, seemingly out of thin air. This is a small bathroom, and I’ve stared and stared at all wall and floor surfaces and see no sign of larvae or where they come from.

Any advice or help appreciated!

rjordan392 · 09-11-2008, 10:53 PM

I can only offer a guess. The pipe connecting the toilet to the main stack must have a small leak. But not enough to show signs. Do you have a cabinet below the sink? I think the flies are making their way through the wall using the access holes where plumbing enters and leaves. Another thought is that you might have animals finding a way inside the house but get trapped and then die in the ceiling or walls. Years ago, I had a bunch of flies on the inside of my basement window screen. I knew right away that they did not enter through any door or window. So there must have been a bird that got in and it entered by the roof area and must have found a way into the basement wall. The wall had a opening at the ceiling area where the animal got stuck above the opening and died.
Start with the sink cabinet and check for openings where they might possibly enter where the pipes are. I think in all homes, there will be enough space arounf these pipes for flies to enter. Place one of those sticky fly traps near the opening and close the cabinet door and check it later.

RippySkippy · 09-12-2008, 11:15 AM

Closing the drains only stops water flow from the sink or tub into the drain. The other path where the little buggers could be doing the happy dance is in the over flow; most sinks have them and the tub definitely does. It could be that there's a bunch of gunk built up in the over flow i.e. soap scum, hair dirt and grunge, that's supporting their life style. Try plugging the over flow spout (blue painters tape) with the drain closed to see if it slows them down. If it does, you know where to start cleaning...

DIYtestdummy · 09-12-2008, 06:55 PM

x2 on the overflow. I put duct tape on one I had in my last apartment. Took care of the problem. You have to get rid of the gunk.

ocoee · 09-13-2008, 12:52 AM

It depends on what you are calling drain flies

I have seen two different types routinely called drain flies

If they are the gnat looking flies then your problem is most probably coming from the drains
Usually they develop in unused drains
If this is a bath that nobody uses the fix could be as easy as running hot water down the drain for about ten minutes a couple of times a month

If it is a frequently used bath then it is probably the over flows

There is a product called Drain Gel that is a biodegradable liquid that you squirt into the effected areas

Drain flies will also live in potted plants if you have any in there or any wet organic matter

If they look like miniature house flies with their wings sticking out to the side they are moth flies and usually are a sign of a pipe leak or standing water under the drain pan or in the wall

marksto · 10-03-2008, 10:52 AM

Thanks to all for the replies. I am happy to say I finally found the source of the drain fly infestation, and it was a surprise as it had nothing to do with drains or other areas you might expect. I'm adding this post in the hopes that someone else with a perplexing infestation like mine will find it helpful.

There is a double hung aluminum window on the long wall in my shower. In between the two panes there is installed a small line of felt to provide a weather seal. It appears that my severe infestation was all stemming from eggs being laid in that little strip of felt.

Once I flipped the window open and soaked that area I started getting dozens of dead flies appearing there by the hour. I had to keep up the soaking with insecticide for about a week, and now I am free of the damn things.

So, the key to drain flies is to keep searching until you find the moist, soft, damp area they breed in.

Bugzilla · 10-05-2008, 07:42 PM

Consistantly (bi-weekly) treating your drains with Drain Gel and an IGR like Archer will eliminate the conducive conditions that allow Drain flies to multiply.

njalex1 · 04-10-2009, 09:48 PM

Marksto,

I have been trying to find the breeding source of these flies for over a month. These have been driving me crazy and it is so difficult to figure out which area they are originating in. I have tried the drain cleaners and put clear tape over them and there is no way they are coming up from there. My house is so clean and spotless.

How did you know to check such an obscure place for the breeding site? What did the breeding site look like so I can start to search in not so obvious places?

Thanks.

lalobr · 10-06-2009, 02:12 AM

We had a pest control come in and fog our bathrooms and hallway. We are extremely clean and have cleaned our bathrooms numerous times. I think it's a drain fly based upon everything we have seen online but not sure. I recently cleaned the 2 bathrooms spotless from ceiling to floor just to see what would happen again (after Fogging). I cleaned during the day waiting for night fall (since this is when they seem to be most active, very active) and then all of the sudden 1 then another and I killed each one after another. Finally I was fed up and stopped. I put fly catchers over my drain and sealed the other drain and pulled the stoppers on my sinks. They were still coming out of nowhere. Anyhow, I stopped killing each one by one last night just to find there were dozens more this morning. I have looked everywhere and am thinking of fogging again and am not sure what else to do!! In fact, I just sprayed our window's like the other POSTER did and we'll see what happens.
Anybody have any suggestions that can help this upset family???

Thank you