: For the past 2 years, around Labor Day, I have house flies coming from a floor drain...they are gone after about 3 weeks. House is only 3 years old, and floor drain is about 20 feet from outside sewer clean out. Could sewer flies be coming up if the contractor did not put a trap at the end of the line before it dumps into the sewer line? Any suggestions?
Sounds like drain flies, they're small black and kinda mothy, they reproduce like crazy and can survive under water, thus even with a trap they swim right up and out...Conduct a web search for drain flies and you'll find articles,,,I've boiled a bunch of water and that slowed them down but I've still got them...good luck