Jun 14, 2012 – Flies and Filth
QUESTION:
My question concerns drain flies. An account has had them for awhile. It is a sand filled slab with sewer pipes running under it. I cannot find an obvious source for the infestation. I injected in the wall void but realize that this alone will not solve the problem. Neither the mens' room nor the ladies' room have any signs of the flies. Is scoping the drain what should be done?
ANSWER:
Drain flies may be less common coming from under slabs than are phorid flies, when plumbing breaks and allows sewage to flow under the slab. There have been massive phorid fly problems resulting from the accumulation of raw sewage in the soils under slabs, and until that source is discovered and repaired and all that contaminated soil removed and replaced the problem will continue. Fly management relies HEAVILY on finding the source, meaning the place where the larvae are feeding and developing. Even spraying over the top of these kinds of breeding sites will have little effect, and more adult flies are going to continue to appear.
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My question concerns drain flies. An account has had them for awhile. It is a sand filled slab with sewer pipes running under it. I cannot find an obvious source for the infestation. I injected in the wall void but realize that this alone will not solve the problem. Neither the mens' room nor the ladies' room have any signs of the flies. Is scoping the drain what should be done?
ANSWER:
Drain flies may be less common coming from under slabs than are phorid flies, when plumbing breaks and allows sewage to flow under the slab. There have been massive phorid fly problems resulting from the accumulation of raw sewage in the soils under slabs, and until that source is discovered and repaired and all that contaminated soil removed and replaced the problem will continue. Fly management relies HEAVILY on finding the source, meaning the place where the larvae are feeding and developing. Even spraying over the top of these kinds of breeding sites will have little effect, and more adult flies are going to continue to appear.
In a sense some of these small flies - phorid, drain, vinegar - are a "sign" telling us that some unsanitary condition exists and must be found and corrected. Attempting to control the problem by killing the adult flies, as you indicate you already know, will be futile. It is an attempt to keep killing the adult flies long enough that the source of the problem finally goes away by itself, and this is not going to happen soon for these flies. If you have already eliminated all the easy answers for drain flies, such as filthy drains or settled water in other places within the living areas, then it would be a good idea to have the plumbing examined. A licensed and qualified plumber should be contacted to run his camera down into the drains to check their quality, and this would not be too terribly expensive. The cost comes when damage to hidden plumbing is found and repairs are needed.
You might be able to narrow the search initially by pinpointing where the flies appear to be coming into the structure, perhaps with the use of UV light traps. This might speed up the evaluation by the plumber.
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