# Drain Flies



## Betharu (Oct 9, 2011)

I have been having a problem with drain flies for several months now. I live outside of Philadelphia. We have had a record breaking couple of months in terms of rain.

My house is a one story rancher - built on a slab - no basement or crawlspace.

The flies seem to be congregating in an outside corner of my deck - near where a door leads into my utility room. 

There is a garden next to the door and gutters above. Some days, they are on the windows of the door, both outside and inside. They also are on the brick wall of my house.

My exterminator was out on Thursday and sprayed. He could not find the source of the flies but gathered that because of the large number in this area, it was most likely at this spot.

Spraying killed a bunch but now they are back again.

As I said before, the ground is VERY wet. Should I work on drying out the garden area - maybe working in some soil or mulch? The gutters were cleaned out before Hurricane Irene but could that be an issue.

HELP! These things are nasty!


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## PAbugman (Jun 29, 2010)

When you say “sewer flies”, does that mean “psychoda” as opposed to being a general catch-all term for small flies? Solving a fly problem, especially the smaller species requires proper identification. If they are in fact sewer flies (psychoda) then I would suspect any stagnant water, sewage, etc. They don’t breed in wet soil unless sewage is present. Is you sewage pipe/septic system in the immediate area? If so, have it inspected for broken pipes, overflowing tank, etc. 

Make sure of the identification of these flies, then post that info. That will point us in the right direction.


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## Betharu (Oct 9, 2011)

*Additional Info*

I do not believe the main drain line is in this area - I do not have a septic tank.

Here are some pics -


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## PAbugman (Jun 29, 2010)

Yep, sewer flies. Psychoda. Learn about them and see if anything fits. Insecticide treatments will only kill emerged adults; won’t stop breeding. There is a source somewhere nearby. These guys aren’t good fliers, so the source is close to where you see them. Any sump pumps or sump drains in the area? Stagnant water is usually the source, but outdoors they are oftentimes linked to sewage pipes, sewers, etc. Rain gutters wouldn’t be an issue. Have you or anyone used animal manure as a fertilizer? Any mushroom farms nearby?


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## Betharu (Oct 9, 2011)

I did have several flower pots in the area that were filled with potting soil that did have alot of standing water. I dumped them into the garden soil. Could that be a source?


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## PAbugman (Jun 29, 2010)

Flower pots and wet soil are not likely sources. Their breeding areas will have noticeably stagnant water if not sewage and such. Drains, drain fields, mushroom farm (rarely, but happens), etc. Learn about psychoda and apply it to your area; see if anything fits.


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