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Discussion Starter #1
I posted a message asking about drain flies in my house about two years ago. At the time I thought I had gotten rid of them by capping an unused shower drain in the basement and cleaning out my drains as best as I could with a bottle brush. Well the next spring they were back and I just spayed from time to time and made sure that drains were not clogged with hair and such. Around this time I also had my septic system cleaned out and when the guy opened a cleanout just outside the house I noticed there were hundreds of drain flies in there. I asked the guy and he said that this was a good thing.

This year the flies are the worst I've seen and one thing new is that we moved the bathroom in our basement. This invloved digging a trench in the basement floor and laying about 20 feet of pipe to service the bathtub, sink and toilet. A vent line was also extended into this new bathroom. I have been seeing a lot of flies in this new bathroom and I know the drains are clean, they have been used very little. I have made sure to pour water in the drains so the traps are full and I don't smell any sewer gas in this room.

Can these flies swim through the water in the traps somehow and make there way into the house or could they maybe be comming in from the vent somehow? I have read that this is often a sign of a broken or leaking drain. In my case the drain is all underslab and heads out to the septic tank still below grade through the basement wall.

At this point I'm just not sure who to call? Should I get a plumber in here to check the traps and such 1st? Should I call an exterminator 1st. I simply can not find a breeding location for these flies other than the septic tank and the line leading from the house the house. Also is this normal to have these in my septic system?

Thanks in advance

Rob
 

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Are these drain flies or phorid flies? Makes a big difference. Drain flies are black with rounded wings that stick out on the side when at rest. Usually hop from one location to another on the wall. Phorid flies look like your ordinary fruit flies but their eyes are red.

No jokes, Rory.

Anyway, drain flies emerge from uncapped sewer lines and yes, they are beneficial in septic systems. The larvae help to degrade waste. They are only a problem when seen inside. If that is what you have, there is an open access to the septic system somewhere in the bathroom as these guys don't travel very far.

As for phorid flies, they are prevalent when waste water is discharged under slabs typically from a break or leak in the discharge line but could also be from a fresh water line break. They breed in soil that is contaminated with waste and can enter rooms around expansion joints at slab edges, cracks in the slab, and around pipe penetrations.

Bottom line, look up on line what you have and that will determine you course of action. I will watch the thread and help where I can.

You guys didn't know I was fluent in bugs, did you? :laughing:
 

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For sewer flies just pour bleach down your drains. :thumbsup:
This will eliminate them from the house.
 

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Sorry, Dusty, that won't work. Drain flies do not emerge from drains that have water in them, only from open drain lines. However, standard ordinary fruit flies WILL breed and feed in water filled drains that are scummy and bleach will work for them. We need to see what his actual pest problem is before suggesting a solution. Nice try, Dusty. :whistling:w00t: :laughing::laughing: :shutup:
 

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sewer fly. Again. I say Bleech
 

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Discussion Starter #6
They appear to be are phorid flies. They have a hump in there backs. They don't have the wings like moth flies. I tried to take a photo, but they are just to small to really focus on my cheap camera.

I looked around again today and found what may be ground zero for the flies. We had a radon fan installed 4 years ago when we moved in and they sealed the sump with clear plexi glass. It was so dusty I could not see through it. When I cleaned it off I noticed that the water was full of dead flies and there were several flying around in there. The caulking around the plexi glass was loose on one side and they are getting in through here. There is a bunch of scum in the sump that they could feed on. I spayed all around the sump pump for now to knock them down a bit. I guess I could drill a hole in the plexi glass and pump some spay down there and then wait and see if they come back.
 
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