I understand the basics of toilet operation and venting, but not sure how to solve this problem. I have a brand new house and toilet and there are septic odors coming from the overfill tube. It is my understanding that when the tank fills, the fill valve fills up the toilet bowl by the small hose that goes into the overflow tube and this water goes into the bowl. So, the overfill tube should only have odors if the bowl has odors or if the s-trap in the toilet is not full of water. There is a vent pipe placed about 3 feet from the toilet off the main 3" line to the septic tank. Even if it was blocked by something, the s-trap should still block odors. Looking for answers. Thanks.