Hi, We have a brand new home with a finished basement. We have a septic system and I notice a smell coming from around the clean out pit in the floor and throughout the basement. The smell is worse when it rains or snow is melting. I can also smell this upstairs when the cold air return is running or the heat/air is running. We have had a smoke test done which was normal. Could there be a broken pipe in the wall somewhere? Another maybe unrelated thing that is odd is that in the middle of winter we have had a lot of flies upstairs in my windows facing east??? Please help know one seems to know what is wrong and I am about to move even though I do not want to. Thank you.