I doubt the ants are coming up from the septic as they would have to "swim" through the p-trap that keeps out the sewer gas. I would look for other entry sources.
TY we will keep checking we bought ant poisons now hope it works
If you are having ants in your house,big or small, mix sugar and Borax and sprinkle around your house. We put it in a sifter and go around the house.It will keep ants away.
Thank you will try it for sure