I have read some of the postings about how to eliminate or at least control sewer flies. We have a septic tank and before I purchase any of the products available I want to make sure they are safe for septic tanks. Does anyone have any suggestions? If possible I would like to treat them asap without having to order something and wait for it to arrive. Thanks for any input.

You won't be putting enough volume in to change any bacterial action in your septic tank. Good luck, Those little pests are a bear to get rid of. I know, I had them for months myself. Good luck, Tom